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Diamond for electronic devices III

Diamond grown by Chemical Vapour Deposition (CVD) or other laboratory methods is rapidly emerging as an important material for new device applications required for the 21st century. Further, large area, high purity diamond substrates have emerged over the past few years, making commercial development of devices a realistic prospect. Many applications are envisaged; in the fields of power electronics, room temperature quantum computing, bio-sensing, bio-interfaces, MEMS-NEMS and high energy radiation and particle detectors to name but a few. It has superior properties for next generation semiconductor applications such as the highest electron and hole mobilities, highest electric field breakdown strength, and a low dielectric constant. In combination with its unmatched thermal conductivity and radiation hardness many applications have been approached meanwhile, and which is at the core of this symposium.  The field is rapidly evolving and it is timely to follow the successful symposia held in 2016 and 2017 with an update on progress in the field at the E-MRS Fall meeting 2018.


Several topics will be of particular interest at this meeting, although papers on all aspects of diamond technology are welcome. These include diamond for power electronics, diamond nano-electronic devices, diamond for quantum applications and diamond for bio-devices. In all cases, man-made single crystalline diamond is used either as ultra-pure layer or semiconducting by boron and phosphorus doping. The growth and deposition of high quality diamond films will therefore be a subtopic at the symposium. Quantum metrology applications (for example, magnetrometry based on NV centres) is of key interest. Doping of diamond is a key topic using both boron and phosphorus. in case of phosphorus and boron doping. The symposium on “Diamond for Electronic Devices II” will include all major activities to realize high quality devices, following on from the very successful symposium at the Fall EMRS meeting in 2016.

Hot topics to be covered by the symposium:

  • Innovative approaches for large area synthetic diamond growth (epitaxy & heteroepitaxy)
  • Diamond devices for power electronics (Schottky diodes, pin, MOS, bipolar transistors).
  • Efficient diamond-based UV emitters and detectors and particle detectors.
  • Doping of diamond (ultra-low, transfer-doping, metallic doping) using hydrogen or metal oxides, phosphorus or boron
  • The realization of ultra-pure diamond substrates
  • Control-removal of surface damage on diamond substrates prior to device fabrication
  • Cellular-diamond interactions for machine-brain interface applications and neurodegenerative disease studies
  • Diamond for imaging and quantum computing – including fundamental studies of colour centres (NV, Ni8, Si, etc), potential quantum devices, and supporting architectures (waveguides, couplers, etc).
  • Diamond films and their functionalization for sensing, imaging and separations, and for SAW , MEMS/NEMS electrochemical and photonic devices.
  • Nanodiamond surface functionalization, nanodiamond chemical-biochemical sensors and nanodiamonds for biological applications

Provisional list of invited speakers

  • Hiroshi Kawarada, Waseda University, Tokyo, Japan
  • Etienne Gheeraert, Institut Neel, CNRS, GRENOBLE, France
  • Hiromitsu Kato, AIST, Tsukuba, Japan
  • Daniel Araujo, University of Cadiz, Spain
  • Fedor Jelezko, Univeristy of Ulm, Germany
  • Yasuo Koide, , NIRIM, Japan
  • Robert Nemanich, Arizona State University, USA
  • Christoph E. Nebel, Fraunhofer-Institute for Applied Solid State Physics (IAF) Germany
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Diamond for High Performance Devices : P Bergonzo
Authors : Raghuraj Hathwar, Manpuneet Benipal, Maitreya Dutta, Franz A. M. Koeck, Mohamadali Malakoutian, Mehdi Saremi, Srabanti Chowdhury, Stephen M. Goodnick, and Robert J. Nemanich
Affiliations : Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287-8806, USA; Department of Electrical Engineering, UC Davis, Davis, California 95616, USA; Department of Physics, Arizona State University, Tempe, Arizona 85287-1504, USA

Resume : The ultra wide bandgap, high hole and electron mobilities, and highest thermal conductivity have indicated diamond as the ultimate power semiconductor. While diamond devices have been designed following principles developed for common semiconductors, the properties of diamond can suggest different configurations that can support high current operation that is sustained and actually improved at high temperatures. This report describes a high current transport regime that takes advantage of drift through intrinsic diamond and high temperature operation that avoids thermal runaway. As these properties are exploited the effects of substrate defects become more evident, and we present arguments of the ultimate performance. Diamond Schottky-PIN diodes with undoped intrinsic drift layers show very high current densities (>500A/cm2) at low forward current voltage (<4V). Examination of the current density vs voltage shows an initial exponential dependence that is followed by a transition to a V**2 dependence. As the voltage is increased further the I-V reaches the linear I vs V dependence determined by ohmic resistance of the contact layers. The V**2 regime has been predicted for space charge limited current in Schottky diodes and has been described by the Mott-Gurney relation. The high current densities indicate an operational mode that is between that of a vacuum diode and a semiconductor Schottky barrier. A simple model is presented which displays the transitions of the three different regimes (exponential thermionic emission, V**2 space charge limited Mott-Gurney, and linear ohmic limited current). Perhaps the most stunning aspect of this effect is that the diode specific on-resistance (RonS) decreases as the voltage increases. Temperature dependent results are presented and described in terms of the model. The outstandingly high performance of the forward current properties of diamond diodes is not typically matched with reverse breakdown, and the role of defects is described for both forward and reverse characteristics, and for projecting the operation of diamond devices on defect free substrates. This research is supported through the NASA HOTTECH program.

Authors : A. Maréchal1, K. Driche2-3-4, J. Letellier2, D. Eon2, N. Rouger6, E. Gheeraert2-4, H. Umezawa2-5
Affiliations : 1Univ. Grenoble Alpes, CNRS, Grenoble INP*, G2Elab, 38000 Grenoble, France; 2Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France; 3Diamond Device Team, Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology, 568-8568 Tsukuba, Japan; 4Graduate School of Pure and Applied Science, University of Tsukuba, 305-8577 Tsukuba, Japan; 5Diamond Materials Team, Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology, 563-8577 Ikeda, Japan; 6LAPLACE, Université de Toulouse, CNRS, Toulouse, France;

Resume : Diamond based unipolar devices are very attractive for power electronics applications. Indeed, diamond shows the highest theoretical figures of merit. In particular, diamond is considered to be the ultimate material for high temperature and low loss, high frequency applications. Tremendous efforts were done to obtain high quality substrates and devices, showing the strong potential for power electronic applications [1]. Several diamond Schottky barrier diodes (SBD) were already reported in the literature [2-6] presenting good performances in reverse operation mode (blocking voltage BV > 1 kV, leakage currents < 10-8 A/cm2 at 1 kV ) as well as in forward bias (>103 at 6 V). However, in order to increase the performances of diamond SBD, one needs to design and fabricate efficient edge terminations (ET) for decreasing the electric field crowding at the main electrode edge. In this way, 1D electrical breakdown of the device is achievable and physical parameters such as the avalanche impact ionization coefficients could be extracted. In this work, we designed and fabricated diamond pseudo-vertical SBD with floating metal rings (FMR). 2.5D TCAD simulations were performed to optimize the device structure, i.e. identifying the number of FMR, their spacing and width . The optimized simulated structure shows a 35 % decrease of the peak electric field at a reverse bias voltage of 250 V as compared to the one without any ET. Static current-voltage analysis and local electric field observation by electron beam induced current (EBIC) will be shown and discussed. The results show that efficient ET techniques are required to take advantage of the full potential of diamond in terms of breakdown capabilities. [1] H. Umezawa, MAT SCI SEMICON PROC, vol. 78, p. 147 156, mai 2018. [2] P.-N. Volpe et al., APL, vol. 97, no. 22, pp. 223501–223501–3, Nov. 2010. [3] A. Traoré et al., APL, vol. 104, no. 5, p. 052105, Feb. 2014. [4] V. D. Blank et al., DRM, vol. 57, no. Supplement C, pp. 32–36, Aug. 2015. [5] V. S. Bormashov et al., DRM, vol. 75, pp. 78–84, May 2017. [6] H. Umezawa et al., APEX, vol. 6, no. 1, p. 011302, 2013.

Authors : Patrik Scajev
Affiliations : Institute of Photonics and Nanotechnology, Vilnius University, Sauletekio al. 3, LT 10257, Vilnius, Lithuania

Resume : Time-resolved differential absorption (DA) and light induced transient grating (LITG) optical techniques were applied for the investigation of nonequilibrium exciton-carrier recombination and diffusion processes in CVD and HPHT diamond. Carrier density range from 1015 to 1020 cm-3 was achieved by combining two-photon and one photon excitations. Temperature was varied in the 10 – 800 K range. The LITG diffusion coefficient peaked at room temperature under low excitation conditions. At lower temperatures it transferred to much lower exciton diffusion coefficient. A strong decrease of diffusion coefficient under higher excitations was explained by exciton formation with a low diffusion coefficient and many body effets, as polyexciton, electron-hole droplet formation. High temperature phonon-limited diffusion coefficient was weakly dependent on carrier density. Low excitation carrier lifetime was ~ 700 ns above 200 K. At lower temperatures however, the decay time reduced by two orders of magnitude, which was explained by the formation of biexcitons, while at higher carrier densities increase of the carrier recombination rate was attributed to Auger recombination of polyexcitons and electron-hole droplets. At high temperatures, the increase of the recombination rate was attributed to phonon assisted excitonic recombination process. The combination of DA and LITG measurements provided excitation and temperature dependent effective diffusion lengths in a 0.3-50 um range.

Authors : Hiromitsu Kato, Masahiko Ogura, Toshiharu Makino, Satoshi Yamasaki
Affiliations : Advanced Power Electronics Research Center, AIST, Tsukuba, Ibaraki 305-8568, Japan.

Resume : Diamond is considered as an attractive semiconductor to open up next-generation electronics based on its unique physical and electrical properties. For instance, the highest breakdown voltage among wide-band-gap semiconductors with high thermal conductivity and high saturation velocity potentially lead to a higher attainable power density. In addition, the excellent spin characteristics of nitrogen-vacancy complexes including long coherence time and optical initialization and read-out properties lead to a potential candidate for single photon source, magnetic sensors, and quantum applications. High quality single crystal diamond growth and impurity doping underlay the design of virtually all these applications. n-type Fermi controlling is still challenging target, since diamond generally prefers to be p-type semiconductor even in an intrinsic diamond. Carbon vacancies including impurity-vacancy complexes are all acceptor-type defects that capture electrons. From the viewpoint of n-type semiconductor diamond, the suppression of these vacancies is one of the most important factors of Fermi controlling as well as suppression of boron acceptors which become compensating donors. On the other hand, from the viewpoint of defect engineering, n-type donors can supply electrons to vacancy defects, leading the stabilization of their charge states. Nitrogen-vacancy complexes have three charge states, and only NV- centers are required for quantum spin applications. In this talk, we would like to discuss the engineering significance of n-type Fermi control from the viewpoints of following two targets. 1) Inversion channel control in diamond/Al2O3 configuration 2) Phosphorus doping for charge-stage control of nitrogen-vacancy complexes Acknowledgements: This work was supported by JSPS KAKENHI Grant Number JP17916364 and JP16776363 and Japan Science and Technology Agency (JST) CREST Grant Number JPMJCR1773, Japan.

15:30 Coffee Break    
NanoDiamond for Electronic Devices : Bob Nemanich
Authors : L Gines, S Mandal and OA Williams
Affiliations : Cardiff School of Physics and Astronomy, Cardiff University, UK

Resume : The production of diamond nanoparticles containing colour centres has attracted increasingly interest in the last years for quantum computation applications. Particularly, the SiV colour centre has highlighted as a promising photon source among other colour centres in diamond, due to its interesting optical properties at room temperature. SiV colour centres acting as single photon emitters can be created through different approaches in in-situ CVD growth by introducing silicon as a solid source or in a gas phase. In this work diamond nanoparticles with custom colour centres were produced from bulk material via milling strategies. First a diamond film containing NV/SiV centres was grown onto a passive substrate, followed by sacrificial etching of the substrate. The resulting diamond film was milled using a planetary mill based on either steel or SiN. The milled material was purified by acid reflux. To measure particle sizes, different slurries containing the diamond nanoparticles obtained were prepared and characterized by using Dynamic Light Scattering (DLS) and Nanoparticle Tracking Analysis (NTA). XPS was also used to qualify the milling process contamination.

Authors : Toshihiko Tanaka(Presenter)[1,3], Yasuhiro F. Miura[2], Tetsuya Aoyama[3], Kazunori Miyamoto[4], Masanobu Uchiyama[3,4], Eiji Osawa[5]
Affiliations : 1. National Institute of Technology, Fukushima College, Iwaki. Fukushima, Japan. 2. Hamamatsu University School of Medicine 3. Elements Chemistry Laboratory, RIKEN Cluster for Pioneering Research (CPR) 4. Graduate School of Pharmaceutical Sciences, The University of Tokyo 5. Nano Carbon Research Institute Ltd.

Resume : Elementary particles of detonation nanodiamond (EPDND) were first revealed by DFT calculations, consisting of some patches of sp2, a mantle of sp2+x, and a core of sp3 carbons [1] and their existence was indicated by the anisotropy of the whiskers from well-dispersed solutions of detonation nanodiamonds (NanoAmando@, NanoCarbon Research Institute Ltd.) [2][3]. A substantial part of the nanodiamonds must be similar both in size and shape and otherwise the linear tapes of the whiskers cannot be explained well. We demonstrate herein that a Langmuir monolayer from arachidic acid (C19H39COOH) induced crystalline precipitates of ultrathin (26 nm) linear tapes from the solutions. The change in surface pressure by an addition of the solution to water sub-phase suggested that an adsorption took place on the monolayer. After opening the trough of the monolayer, we found innumerable ultra thin rectangular tape pieces on the water surface. We deposited them on glass or silicon plates through a horizontal method by using a natural evaporation of water for a few days. After the air dry, we observed their uniform birefringence and the Raman spectra of nanodiamonds from the tapes. They have never been found without the acids, thus showing that the acids work as a nucleating agent or a flocculant. [1] A. S. Barnard, E. Osawa; Nanoscale 6, 1188 (2014). [2] E. Osawa; Diamond & Related Materials. 16, 2018–2022 (2007). [3] T.Tanaka, et al, Abstract of the 54th FNTG Symposium, 28(2018).

Authors : Joseph O. Welch, Abdul Afandi and Richard B. Jackman
Affiliations : London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH, U.K

Resume : Schottky-barrier diodes are one of the cornerstones of modern high-power switching electronics, along with the diamond transistors. The combination of the two in terms of diamond technology would enable the handling of large currents with high efficiency, compared semiconductor devices formed from other wide band-gap materials. It is notoriously difficult to achieve the low boron doping levels required for effective device operation by purposeful doping by the use of boron-containing gases during CVD growth. This paper addresses a novel, and new, method for making diamond devices through the use of ‘doped’ nanodiamonds (NDs) overgrown with an intrinsic diamond layer. This approach offers the prospect of an inexpensive, safe, method for diamond device fabrication for high power applications. We have previously published evidence for how B-doped detonation nanodiamonds (B-DNDs) can display effective semiconducting properties [1]. In the current study this form of diamond has been used along with chemically synthesized B-doped NDs and so-called ‘crushed’ B-doped diamond nanodiamonds for the formation of highly effective Schottky Barrier diamond diodes (SBDs). All three types of SBD devices exhibit slightly different properties; however, they all confirm the possibility of purposeful low-level doping of diamond films using previously doped nanodiamond ‘seeds’. This eliminates the need for using diborane or other boron gas sources during CVD growth. Whilst initial results were based on a single ‘doped’ layer through the use of B-ND seeds prior to intrinsic growth, preliminary results suggest that multi-layers of B-ND seeds/i-Diamond/B-ND seeds/i-Diamond etc.., can enable highly effective rectification and high current switching capabilities. This is an entirely new way of making inexpensive high-power diamond diodes, and ultimately transistors, and the prospects for this technology will be addressed in detail. [1] Nanodiamonds for device applications: An investigation of the properties of boron-doped detonation nanodiamonds Abdulkareem Afandi, Ashley Howkins, Ian W. Boyd & Richard B. Jackman Scientific Reports 8, 3270(2018), doi:10.1038/s41598-018-21670-w

17:00 Break    
Poster Session : Daniel Araujo
Authors : Gergo Thiering, Adam Gali
Affiliations : Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, POB 49, H-1525, Hungary; Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111, Budapest, Hungary

Resume : The impurities of diamond are promising candidates as building blocks for quantum computing. In particular, the high-spin negatively charged nitrogen-vacancy defect (NV) in diamond has become a leading contender in solid-state quantum information processing. The initialization and readout of the spin is based on the spin-selective decay of the photo-excited electron to the ground state which is mediated by spin-orbit coupling between excited states states and phonons. While there are models describing [1,2] the decay from the dynamic Jahn-Teller [3] (JT) 3E triplet, there is little known [4] about the decay from the 1E singlet. This is a critical step toward understanding spin polarization and readout of this quantum bit. Here we show a theoretical model for the intersystem crossing (ISC) of the 1E singlet state of NV. We find that the singlet states are coupled with pseudo-JT interaction [1] modulated by diamond phonons. Our model suggests that this coupling governs the ISC rate from the 1E singlet to the 3A2 triplet ground state. We also suggest that the pseudo-JT produces the anomalous difference in absorption and emission sideband of the 1.19-eV optical line between the two aforementioned singlets. We yield quantitatively good parameters for the model via ab initio supercell density functional theory (DFT) calculations. We determined the strength of pseudo-JT interaction up to 10 phonon limit in the Born-Oppenheimer basis. Our theoretical model [5] is verified by the good agreement with the theoretical and observed absorption and luminescence spectrum of the singlets. Finally, we study the spin-selective and ISC rates (Γz and Γ±) from the 1E state towards the ms=±1 or ms=0 substate of 3A2 triplet by our ab-initio data, respectively. By taking our ab-initio data and the observed 1.19 eV energy gap between the singlets, we were able to reproduce the 2-3 MHz ISC rate [6,7], in addition to the temperature dependence of the singlet lifetime. In summary, we provide deep insight in understanding the optical spin-polarization process of NV center in diamond. 1. M. L. Goldman, et al. Phys. Rev. Lett. 114, 145502 (2015). 2. G. Thiering, A. Gali Phys. Rev. B 96, 081115 (2017). 3. I. Bersuker, The Jahn-Teller effect (Cambridge University Press, 2006). 4. M. W. Doherty, Physics Reports 528, 1 (2013). 5. G. Thiering, A. Gali Phys. Arxiv: 1803.02561 (2018) 6. V. M. Acosta, et al. Phys. Rev. B 82, 201202(R) (2013). 7. L. Robledo, et al. New Journal of Physics 13, 025013 (2011)

Authors : L. Drbohlavová, A. Talbi, V. Mortet
Affiliations : Institute of Physics, Academy of Sciences Czech Republic v.v.i, Prague 8, Czech Republic, Czech Technical University, Faculty of Biomedical Engineering, Kladno, Czech Republic; Univ. Lille, Centrale Lille, UVHC, ISEN, LIA LICS/LEMAC - IEMN UMR CNRS 8520, F-59000; Institute of Physics, Academy of Sciences Czech Republic v.v.i, Prague 8, Czech Republic, Czech Technical University, Faculty of Biomedical Engineering, Kladno, Czech Republic

Resume : Nowadays the detection of pathogens is an inherent part of environmental or food industry safety. In spite of good selectivity of conventional methods, they are time consuming and labor intensive. Biosensors are good candidates for real-time monitoring and fast detection of pathogenic agents ‎[1]. Acoustic devices are in the focus of researchers for bio-sensing applications using appropriate surface functionalization ‎[2]. Love wave surface acoustic wave (LW-SAW) sensors possess high sensitivity in liquid ‎[3]. Acoustic energy is confined in the guiding layer close to the sensitive surface, and the energy is not radiated in the liquid due to using pure shear wave with displacement parallel to the surface ‎[4]. Integration of diamond layer brings many favorable properties such as biocompatibility, various biomolecules attachment and prolonged stability of attached biomolecules ‎[5]‎[6]‎[7]. For these reasons, we theoretically investigated properties of layered structures Diamond/SiO2/36°YX LiNbO3 and Diamond/SiO2/ST-cut quartz for potential biosensor applications. Theoretical calculations were carried out with normalized thickness hSiO2/λ in the range of (0.01 – 1) and different thicknesses of the diamond coating. Legendre and Laguerre polynomial approach of wave propagation in layered structures ‎[8] was used for determination of the phase velocity vp and electromechanical coupling coefficient K2 dispersion curves. We also investigated the sensitivity of Diamond/SiO2/ST-cut quartz and Diamond/SiO2/36°YX LiNbO3 structures by using 100 nm thick PMMA film surface loading. The optimal sensitivity of the Diamond/SiO2/36°YX LiNbO3 is obtained for silicon dioxide normalized thickness hSiO2/λ between 0.3 and 0.6 for all tested diamond thicknesses. In this range of normalized thicknesses hSiO2/λ, the electromechanical coupling coefficient is steeply decreasing from 15 % to 5 %. The diamond/SiO2/ST-cut quartz structure simulation results show similar behavior. The highest sensitivity and K2 of this structure are obtained for normalized thickness hSiO2/λ between 0.2 and 0.6. Results of this theoretical study show it is possible to fabricate LW-SAW devices with a very thin diamond coating without significant loss of the sensitivity. Properties of LW-SAW devices fabricated on 36° YX LiNbO3 substrate will be presented and compared with theoretical results and previous studies on LW-SAW devices fabricated on ST-cut quartz substrate [9]. [1] SINGH, A. et al., Biosensors and Bioelectronics, 2009, 24(12), 3645-3651. [2] LÄNGE, Kerstin et al. Analytical and Bioanalytical Chemistry 2008, 391(5), 1509-1519 [3] GRONEWOLD, Thomas M.A., Analytica Chimica Acta, 2007, 603(2), 119-128. [4] RABUS, D., et al., Journal of Applied Physics, 2015, 118(11), 114505 [5] KRUEGER, Anke a Daniel LANG., Advanced Functional Materials, 22(5), 890-906 [6] Vadym N. Mochalin, et al., Nature Nanotechnology, 7(1):11–23. [7] VAIJAYANTHIMALA, V., et al., Biomaterials, 33(31), 7794-7802 [8] BOU MATAR, Olivier, et al., The Journal of the Acoustical Society of America. 2013, 133(3), 1415-1424 [9] Drbohlavová, L., et al., Proceedings 2017, 1, 540.

Authors : V. Mortet (1,2), Z. Vlčková Živcová (3), M. Davydova(1), A. Taylor(1), D. Machon(4), O. Frank(3)
Affiliations : (1) Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, 182 21, Prague 8, Czech Republic (2) Czech Technical University in Prague, Faculty of Biomedical Engineering, Sítna 3105, 272 01, Kladno, Czech Republic (3) J. Heyrovsky Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejskova 3, 182 23, Prague 8, Czech Republic (4) Université de Lyon, F-69000 Lyon, France and Institut Lumière Matière, CNRS, UMR 5306, Université Lyon 1, F-69622 Villeurbanne, France

Resume : Raman spectroscopy is a simple and non-destructive characterization technique that can be used to estimate the boron concentration in highly boron-doped diamond with metallic electrical conductivity [1,2]. While the Raman spectrum of boron-doped diamond is well described with three main bands at 500 cm-1 (B1), 1200 cm-1 (B2) and the Fano shaped diamond zone-center phonon line (B3), there is no accurate consensual description of the origin of the B1 and B2 bands. In this work, we study the Raman spectrum of epitaxial boron-doped diamond layers with various boron concentrations, excitation wavelengths, and temperatures to further understand the mechanism at the origin of this characteristic Raman spectrum. We will present a simple analysis that accurately describes measured Raman spectra of boron-doped diamond layers based on electronic Raman scattering and Fano effect models. We will demonstrate the Raman spectra result of the interaction of the diamond phonon density of states and the electronic Raman scattering. Based on this model, we will present and discuss the evolution of the electronic Raman scattering, the characteristic bands of the boron doped diamond Raman spectrum and the Fano asymmetric parameters as a function of the excitation wavelength, the temperature, and the boron concentration. Acknowledgment: This work was financially supported by project 17-05259S of Czech Science Foundation and the J.E. Purkyně fellowship awarded to V. Mortet by the Czech Academy of Sciences. [1] V. Mortet, Z. Vlčková Živcová, A. Taylor, O. Frank, P. Hubík, D. Trémouilles, F. Jomard, J. Barjon, L. Kavan, Insight into boron-doped diamond Raman spectra characteristic features, Carbon. 115 (2017) 279–284. doi:10.1016/j.carbon.2017.01.022. [2] M. Bernard, A. Deneuville, P. Muret, Non-destructive determination of the boron concentration of heavily doped metallic diamond thin films from Raman spectroscopy, Diamond and Related Materials. 13 (2004) 282–286. doi:10.1016/j.diamond.2003.10.051.

Authors : Barbora Jakubcová, Jana Turňová, Ondřej Řehounek, Jiří Polák, Andrea Mineva, Andrew Taylor, Pavel Hubík, Václav Petrák and Vladimíra Petráková
Affiliations : Faculty of Biomedical Engineering, Czech Technical University in Prague, nam. Sitna 3105, 272 01, Kladno, Czech Republic; Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21, Prague, Czech Republic.

Resume : The ability to form an efficient interface between material and neural cells is a crucial aspect for construction of neuroelectrodes. Diamond offers material characteristics that could, to a large extent, improve the performance of neuroelectrodes. The greatest advantage of diamond is a large variety of material and surface properties such as electrical conductivity, surface morphology, and surface chemistry. Such a variety of material characteristics can lead to various cellular responses. Here we compare survival, adhesion, and neurite formation of primary neurons on diamond thin films of various morphologies and treatments with several types of polymers commonly used to enhance cell adhesion. We found that the variation of surface roughness of nanocrystalline diamond film when coated with polymer does not have a major influence on neuron survival or adhesion. The adhesion of neurons can be influenced by the selected type of polymer coating. High molecular weight of polyethylenimine resulted in lower viability, adhesion and neurite formation. The addition of laminin to treated films did not lead to significant improvements in neuron adhesion and neurite development. Our findings emphasize the importance of the correct polymer treatment over morphological properties of diamond thin films as a material for forming interfaces with primary neurons. This work has been accepted for publication in Advanced Engineering Materials.

Authors : Massimilano Ramsay, Joseph O. Welch and Richard B. Jackman
Affiliations : London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH, U.K

Resume : The realisation of solid state devices that offer the ability to sense a range of chemicals / bio-chemicals within the marine environment with high sensitivity is a key enabling technology for many applications. If these devices can be enabled for remote communication even more potential applications are encountered. In terms of maritime vehicles, devices that monitor chemicals / bio-chemicals that encounter the vessel would be of significant interest in terms of bio-fouling and corrosion studies, and devices that could detect marine bound chemicals as local signature of recent marine activity, either with devices on the vessel or trialled behind the vessel could enhance detection and surveillance capabilities. Using the communication technologies often described as the ‘internet of things’ remotely deployed solid state (miniature) sensors could enhance surveillance capability in the wider marine environment. Limitations that prevent current technologies being deployed in such a way include the lack of resilience of the sensor materials to the marine environment, a lack of sensitivity and selectivity when in sea-water and a lack of miniaturised technology, whereby driver and read-out electronics is integrated with the sensing platform. Diamond a wide band gap (5.5eV) semiconductor material with extreme properties electronic, optical, thermal, hardness and chemical properties. Not only does this make a sensor platform the most suitable in terms of resilience in a marine environment, but diamond has also been shown to resist bio-fouling more than other materials [Electrochimica Acta 55 (2010) 6586–6595]. Diamond is now a commercially available Engineering material, with high purity diamond (grown by CVD methods) being offered a number of suppliers at modest cost [see for example,]. Diamond can be doped with boron to reveal p-type semiconducting properties; at high boron concentrations diamond becomes a quasi-metal enabling it to be used as an electrode material [phys. stat. sol. (a) 154, 423 (1996)]. Diamond displays the highest ‘electrochemical window’ of any electrode material in water (the potential at which the redox breakdown of water occurs) meaning that diamond devices can operate at higher voltages than those made conventional materials. Any solid state detector that aims to look at organic or bio-organic materials immediately encounters the issue that they all contain carbon, rendering differences seen between species difficult to determine. One spectroscopy that overcomes this problem is Raman. Raman spectroscopy is a technique for looking at molecular vibrations, and hence the identification of the types of chemical bonds present. This information can then be used to identify the chemical composition of the material being examined. A brief overview of the technique will be offered and recent results presented shoiwing that diamond is perhaps unrivalled as a semiconductor for this application. Acknowledgments BAE Systems Maritime and the UKs Engineering and Physical Sciences Research Council (EPSRC) are gratefully acknowledged for the award of a ‘CASE’ PhD studentship to MR. BAE Systems are also thanked for financial support for the project.

Authors : A. C. Pakpour-Tabrizi1, F. Mazzola2 J.A. Miwa3 F. Arnold4 M. Bianchi4 P. Hofmann3, J. W. Wells2 and R. B. Jackman1
Affiliations : 1London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH, U.K 2Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway 3Department of Physics and Astronomy, Interdisciplinary Nanoscience
Center (iNANO), Aarhus University, 8000 Aarhus C, Denmark 4Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark

Resume : High quality single crystal diamond with thin δ-shaped boron-doped epilayers have been thought to offer a viable approach towards high speed, high power and high temperature applications. δ- doping diamond has been conjectured to achieve high mobilities and carrier concentrations, proper- ties of real interest for electronic applications. Taking advantage of diamond’s thermal and electronic properties, thin films can be incorporated into realistic nanoscale devices more easily than the parent bulk system. Using angle-resolved-photoemission spectroscopy (ARPES), we uncover the electronic structure of bulk and thin films (≈ 2 nm) of boron-doped diamond. Surprisingly, the ARPES measurements do not reveal any significant differences for these systems, irrespective of their physical dimensionality. This suggests that it is possible to grow nearly atomic-scale structures whilst still preserving the properties of bulk diamond facilitating the use of thin films diamond for devices which necessitate nearly atomic-scale components. ARPES measurement collected at photon energy 170 eV for a thick (> 1μm) boron-doped diamond film show- ing the binding energy (EB) dispersion as function of ⃗k||; the measurement corresponds to the band structure of boron- doped diamond acquired along the green line shown in the inset representing the BZ of diamond. Three bands (labeled as A, B and C) disperse close to the Fermi level (EF ), with ‘A’ crossing EF , hence contributing to the metallic character of the sample. Additional horizontal bands (H1 and H2, see horizontal guide depicted by the dashed lines) are detected: we believe that these bands are an artifact coming from the edges of the Brillouin zone, where the electronic states have exceptionally high intensity and therefore such intensity can scatter across to the Brillouin zone center.

Authors : Maeve McLaughlin, Richard B. Jackman
Affiliations : London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London, WC1H 0AH, UK

Resume : Mercury naturally exists in crude oil in quantities ranging from 0.1 to 20,000 µg/kg and is released into the atmosphere and wastewater streams during extraction and processing[1]. Even in trace amounts mercury poses a severe threat to both human health and the environment because it is highly toxic and tends to form complexes with ligands of biological matter, leading to an accumulation in the food chain[2]. The World Health Organisation guideline for the maximum safe quantity of mercury in drinking water is 6µgl-1 ca. 30 nM[3]. It is imperative that trace contamination of potable water by oil processing wastewater streams is identified in situ. This can be achieved through electrochemical techniques, which also have the advantage of relative low cost and simplicity compared to optical methods. Boron doped diamond (BDD) electrodes are particularly well suited for the trace detection of mercury due to the wide electrochemical window, low background currents, resistance to fouling and stability at extreme temperature, pressure and pH associated with the material[4]. In this work square wave anodic stripping voltammetry (SWASV) was used with a BDD working electrode in a nitric acid electrolyte (0.1 M). This system is considered to be one of the most sensitive electro-analytical techniques for trace analysis, with detection of mercury recorded here in the pico-molar range. To improve the sensitivity of mercury detection the BDD electrode surface was decorated with gold nanoparticles, which act catalytically during the pre-concentration step of the SWASV measurements. A comparison study was made between drop-casting the nanoparticles and depositing thin films of gold which were then de-wet into nanoparticles by annealing in an inert atmosphere. Through the annealing method a range of nanoparticle sizes and dispersions on the electrode surface were investigated, to identify the optimum gold nanoparticles for catalytic action in sensing mercury by SWASV. We have successfully detected mercury at pico-molar concentrations and initial results show increased sensitivity with smaller gold nanoparticles (<15 nm) on the BDD surface. [1] Lang, D. et al. “Mercury arising from oil and gas production in the United Kingdom and UK continental shelf” IKIMP (2012)

Authors : Hiromitsu Kato1*, Takatoshi Yamada2, Masahiko Ogura1, Toshiharu Makino1, Satoshi Yamasaki1
Affiliations : 1 Advanced power electronics research center, AIST, Tsukuba, Ibaraki 305-8568, Japan 2 Nanomaterials research institute, AIST, Tsukuba, Ibaraki 305-8565, Japan *

Resume : Carbon-based materials are strongly expected to be applied to electron emitter cathodes. CNT and graphene with low-dimensional nano-materials composed of sp2 bonds can be possible with higher emission current, while it is vulnerable to heat and shock and long-term stability is one of the remained issues. Diamond has attracted attention as a material of an electron source because of their potentially low or negative electron affinity. Diamond possesses the highest hardness of the material and is composed of strong C-C bonds sp3 structure, which the material stability and reliability are very high. On the other hand, conductivity control with impurity doping has still difficulties than other materials. Nano crystal diamond (NCD) is a material composed of a mixed structure of sp2 and sp3 bonds and attracts attention as one of materials that can exploit both these features. Doping of phosphorus impurities as well as boron and nitrogen has become possible in recent years, and technology for lowering resistance has also been established. The resistivity of NCD can be reduced by almost 2 orders of magnitude lower than that of single crystal diamond. In addition, NCD can be formed on various substrates such as silicon substrate, metal substrate, glass, etc., leading the high controllability of structure and area-size enlargement. Many researches on electron emission characteristics and thermionic emission characteristics have reported with attractive properties, i.e., low work function, high thermionic emission properties, low threshold voltage, etc. In this paper, we focused on phosphorus-doped NCD films and discuss their structural characterization from cross-sectional TEM and electron energy loss spectroscopy study. Acknowledgements: This work was supported by JSPS KAKENHI Grant Number JP16776363.

Authors : Péter Udvarhelyi, Gergő Thiering, Elisa Londero, Adam Gali
Affiliations : Department of Biological Physics, Loránd Eötvös University, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary; Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary; Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary; Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary

Resume : Paramagnetic point defects in diamond are candidates for quantum bit and quantum information applications. The N2V defect is formed by an aggregation of neighbor substitutional nitrogen atoms trapping a mobile vacancy [1]. The defect in its neutral charge state was assigned to H3 color center [2] and W26 ESR center [3]. As the H3 center exhibits a singlet ground state and an optically accessible metastable triplet state we wished to explore the properties of the N2V defect for quantum memory applications. We have characterized this defect in diamond by means of ab initio methods relying on density functional theory (DFT) calculated parameters of a Hubbard model Hamiltonian. It is shown that this approach appropriately describes the energy levels of correlated excited states of this defect using only DFT wave function and energies. With magneto-optical parameters determined by means of DFT calculations that go beyond the conventional Kohn-Sham DFT methods, we demonstrate that optical spin polarization of the triplet state and spin polarization transfer to the existing nuclear spins is principally feasible. Thisway a long-living quantum memory may be realized with N2V defect. [1] A. Mainwood, Phys. Rev. B 49, 7934 (1994). [2] R. Jones, P. R. Briddon, S. Öberg, and V. J. Torres, in Defects in Semiconductors 17, Materials Science Forum Vol. 143 (Trans Tech Publications, Zürich, 1993), pp. 45–50. [3] J. A. van Wyk and G. S. Woods, J. Phys.: Condens. Matter 7, 5901 (1995).

Authors : Khaled Driche, Hitoshi Umezawa, Masahiko Ogura, Toshiharu Makino, Hajime Okumura, Etienne Gheeraert
Affiliations : Universite Grenoble Alpes CNRS, Institut NEEL Graduate School of Pure and Applied Science, University of Tsukuba AIST, Advanced Electronics Research Center

Resume : Diamond is an attractive material for optoelectronics and power devices due to its outstanding properties such as high critical field, high hole mobility, high thermal conductivity and low dielectric constant. Diamond Schottky barrier diodes with blocking capabilities up to 10 kV have been already reported [1], and diamond Field Effect Transistors through MOSFETs [2] and MESFETs [3] have been recently investigated. Among them, diamond MESFETs are well suited for high frequency and high power devices. In this work, diamond MESFETs have been fabricated and characterized. Heavily boron doped layer was grown selectively to reduce source and drain contact resistance. The gate length LG varies from 10 μm to 30 μm and the gate to drain length LGD from 30 μm to 50 μm. The drain current was 1.4 μ @0V with a back-gate biased at -40V to reduce the depletion region at the substrate interface. The measurements were done under vacuum and light. In the dark, there is no current flowing corresponding to an off-state. A breakdown voltage over 4 kV is expected for this device. The presence of trap in the diamond bulk or at the interface could be one reason to this activation by light. Indeed, a shift of the threshold voltage was observed when performing current-voltage measurement between two consecutive sources. This phenomenon has already been reported for gallium nitride GaN and silicon carbide SiC transistors [4]. Wavelength dependency will be discussed in the presentation. [1] P. Volpe et al., Phys. Status Solidi. 207 (2010) 2088–2092. [2] Y. Kitabayashi et al., IEEE Electron Device Lett. 38 (2017) 363–366. [3] H. Umezawa et al., IEEE Electron Device Lett. 35 (2014) 1112–1114. [4] S.C. Binari et al., IEEE MTT-S Int. Microw. Symp. Dig. 3 (2002) 1823–1826.

Authors : Shinya Ohmagari, Hitoshi Umezawa, Hideaki Yamada, Akiyoshi Chayahara, Nobuteru Tsubouchi, Yoshiaki Mokuno, and Daisuke Takeuchi
Affiliations : Advanced Power Electronics Research Center, AIST, Japan

Resume : With the superlative physical properties of a high breakdown field strength, high carrier mobility, and high thermal conductivity, single-crystal diamond has attracted much attention as a material for next-generation low-loss power devices. High switching capabilities have been demonstrated for both unipolar and bipolar devices, Schottky rectifiers, p-i-n diodes , and field-effect transistors (FETs). However, most of these characteristics were reported using insulating substrates. To enhance the device performance further, the development of low-resistivity diamond substrates is required. Vertical architectures can withstand very high currents with large electrodes on the front and back sides of substrates. In addition, the potential distributions within vertical structures are more favorable than those in lateral architectures to support high voltages. In this study, heavily B-doped p+ diamond (100) films were grown by hot-filament CVD. Low resistivity (<0.003 Ohmcm) was successfully realized with high-rate growth conditions (1–4 micron/h). The as-grown film surface exhibited step-bunching faces without non-epitaxial grains; lateral growth was maintained over thick films (>100 micron). Freestanding crack-free films were prepared by removing the seed substrates via laser-cut and mechanical polishing processes. The X-ray diffraction rocking curve (004) spectrum showed the full-width at half maximum value of 25 arcsec, equivalent to that of the seed substrates employed.

Authors : H. Umezawa, K. Driche, E. Gheeraert
Affiliations : Institute Neel/CNRS, AIST; Institute Neel/CNRS, AIST, University of Tsukuba; Institute Neel/CNRS, University of Tsukuba

Resume : Electrical field enhancement at the edge of the Schottky electrode on diamond under reverse bias condition was characterized by electron beam induced current (EBIC) measurement. The increase of the EBIC signal was clearly observed at the edge of the electrode when the electrical field was increased more than 0.9 MV/cm. The high EBIC signal area corresponds to the laterally expanded depletion layer (LDL). We also confirmed that the EBIC signal was not uniformly distributed in LDL but very bright spots, such as hot spots, existed. The leakage current of the diodes corresponded to the bright spots at the edge of the electrode. The position of the hot spots correspond to that of the roughness at the periphery of the Schottky electrode which have caused during the lift-off process [1]. We extracted carrier multiplication factor by analyzing EBIC intensity and applied electrical field on the devices. The value is lower than that of the reported up to now. Reference: [1] H. Umezawa, H. Gima, K. Driche, Y. Kato, T. Yoshitake, Y. Mokuno, and E. Gheeraert, "Defect and field-enhancement characterization through electron-beam-induced current analysis," Applied Physics Letters, 110, 182103 (2017).

Authors : Viktor Ivady 1), 2), Igor A. Abrikosov 2), 3), and Adam Gali 1), 4)
Affiliations : 1) Wigner Research Centre for Physics, Hungarian Academy of Sciences, PO Box 49, H-1525, Budapest, Hungary; 2) Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden; 3) Materials Modeling and Development Laboratory, National University of Science and Technology `MISIS', 119049 Moscow, Russia; 4) Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary;

Resume : High degree hyperpolarization of arbitrary samples and nuclear magnetic resonance (NMR) agents is of great importance for sensitivity enhanced NMR sensing and imaging measurements for decades. Protocols use only optical illumination and operate even at room temperature are of highest importance. Here, we report on the combined ab initio and model spin Hamiltonian theoretical model for a recently reported hyperpolarization measurement on a diamond sample consisting N3V and P1 centers. [1] Our theory explains the experimental observations and show how the initial static electron spin polarization is dynamically distributed between paramagnetic defects and nuclear spins. [1] B. L. Green, Phys. Rev. B 96, 054101 (2017)

Authors : Victor Strelchuk, Iurii Nasieka, Yuriy Stubrov, Stanislav Dudnik, Vasiliy Gritsina, Oleg Opalev, Konstantin Koshevoy, Vladimir Strel’nitskij, Mykola Boyko
Affiliations : Victor Strelchuk, Iurii Nasieka, Yuriy Stubrov, Mykola Boyko - V.Ye. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 45 Pr. Nauky, Kyiv, 03028, Ukraine Stanislav Dudnik, Vasiliy Gritsina, Oleg Opalev, Konstantin Koshevoy, Vladimir Strel’nitskij - National Science Center “Kharkov Institute of Physics and Technology”, 1, Akademicheskaya St., Kharkov, 61108, Ukraine

Resume : Previous works devoted to preparation of [100] and [111] textured diamond films with (100) and (111) faceted microcrystals as well as to search for the specific technological regimes allowing the relatively stable growth of diamond single crystals (grains) with the mentioned faceting have been analyzed. General features responsible for the growth of freestanding diamond grains of certain faceting without additional nucleation on the faces have been discussed. The PE CVD method with magnetic field discharge stabilization was applied for the growth of arrays of freestanding diamond grains (island films) as well as continuous films on Mo and Si substrates, respectively. Raman, SEM, XRD, PL and SIMS methods were used for search of the difference in the defect states embedded into (100) and (111) faceted grains. Keywords: Diamond microcrystals; PE CVD technique; Raman scattering; Fourier-transform infrared spectroscopy; (FTIR); Photoluminescence; Scanning electron microscopy (SEM).

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Diamond Colour Centres as Sensing Devices : Adam Gali
Authors : T. Trost, V. Zürbig, C. Widmann, C. Giese, C.E. Nebel
Affiliations : Fraunhofer-Institute for Applied Solid State Physics (IAF), Tullastr. 72, D-79108 Freiburg, Germany

Resume : Quantum technology based on diamond requires in nearly all cases ultra-pure layers, with minimized defect densities and isotopically enriched (12C) compositions. For quantum magnetometry, the NV center is very promising due to its unmatched properties. In the literature one can find spin coherence times (T2) up to seconds for NV centers generated deep in the diamond layer. However, for NV centers close to the surface in the range 5 to 20 nm, the spin coherence time constant decreases to typically about 10 microseconds. The reasons for this phenomenon are attributed to surface and near-surface damage generated by mechanical polishing and plasma induced etching. To overcome this limitation one can perform homoepitaxial overgrowth of low defect density diamond layers of typically 1 to 10 micrometer thickness before NV incorporation. The T2 time will increase to properties comparable to the bulk. This technique can offer advantages for devices which require smooth surfaces. Vertical diamond waveguide structures however, which are required for scanning NV-magnetometry, can up-to-now only be produced by plasma etching and are therefore of limited quality. In this contribution we introduce a bottom-up technique to generate diamond tips by diamond growth. Firstly, we grow ca. 10 micrometer thick ultra-pure diamond on a [100] diamond seed crystal. Then a Ti mask is deposited, followed by an O2-plasma etching step to form diamond tips of typical 200 nm diameter and ca. 3 micrometer of length (top-down approach). These tips are used to generate a 3D diamond growth around the tips, forming (111) and (100) facets. We use our specifically designed load-lock PECVD reactor which is optimized for the deposition of thin high-quality diamond layers. Dependent on our selected growth parameters we can tune the and parameters of the growth regime to grow tips with pyramidal shapes either with sharp tips or with (100)-oriented mesas. We will introduce our results in detail based on scanning electron microscopy imaging, atomic force microscopy and and parameter growth models.

Authors : Nicole Raatz, Tobias Luehmann, Roger John, Jan Meijer, Sebastien Pezzagna
Affiliations : Nuclear Solid-State Physics, University Leipzig, 04103 Leipzig, Germany

Resume : Most of modern sensing or quantum information applications based on optical centres in diamond are generally conducted in electronic- or quantum-grade material grown by chemical vapour deposition (CVD). Despite very low amounts of nitrogen and boron impurities (in the ppb regime or less), such material is still inherently rich in hydrogen. Little is known concerning the homogeneity of the hydrogen concentration within one sample or from one sample to the other. However concentrations between a few ppm and a few hundreds of ppm are reported, measured by secondary ion mass spectrometry (SIMS). Hydrogen is therefore the main impurity in such samples. Recently, it was shown that nitrogen-vacancy (NV) centres (and possibly other optical centres) are fragile in what concerns hydrogen diffusion, because they can be passivated, leading to the formation of NVH centres. These are very stable and the NV centres cannot be re-activated even using high temperature treatments. As well, electronic devices using p-type or n-type doping may suffer from the presence of hydrogen which can passivate the dopants, leading to less efficient devices. On the other hand, high-pressure high-temperature (HPHT) diamonds are expected to contain very little amounts of hydrogen. In this work, we study the role of hydrogen on the formation and the properties of optical centres created by ion implantation and annealing. We discuss the results obtained in the purest CVD and HPHT samples, as well as the co-implantation of hydrogen. Finally, we quantify the hydrogen passivation of optical centres in different experimental conditions and samples.

Authors : L. Rigutti*, L. Venturi*, J. Houard*, A. Normand*, E. P. Silaeva*, M. Borz*, S. A. Malykhin**, A.N. Obraztsov*** , A. Vella*
Affiliations : * Normandie Univ, UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, 76000 Rouen, France ** University of Eastern Finland, Department of Physics and Mathematics, Joensuu 80101, Finland *** M V Lomonosov Moscow State University, Department of Physics, Moscow 119991, Russia

Resume : In this work we report a method to perform piezo-spectroscopy of nanoscale systems by electrostatic field regulation. In particular, we studied diamond nanoscale needles containing color centers [1]. The polarization-resolved micro-photoluminescence (-PL) of these centers is studied within an Atom Probe Tomography (APT) instrument. The application of a high electrostatic field at the apex of monocrystalline diamond nanoscale needles induces an energy splitting of the photoluminescence lines of color centers [2]. The splitting of the zero-phonon PL line of the NV0 defect has been studied as a function of the voltage applied to the tip. The measured quadratic dependence of the energy splitting on the applied voltage, reported for the NV0 defect, corresponds to the stress generated on the metal-like apex surface by the electrostatic field. Tensile stress up to 7 GPa has thus been measured in the proximity of the needle apex. The intensity of the stress, measured on the diamond nanoneedles, is higher as the apex radius of the diamond nanotips is smaller. In perspective, these results disclose the possibility of correlative studies of structural and optical properties of color centers by exploiting the 3D atomic scale imaging capabilities of APT. The application of the method to other color centers will be also discussed. [1] Kurtsiefer et al.. Phys. Rev. Lett. 2000, 85 (2), 290–293. [2] L. Rigutti, et al., Nano Lett., 17 (12), 7401-7409, 2017.

Authors : L. Toraille, M. Lesik, T. Plisson, J. Renaud, L. Rondin, T. Debuisschert, O. Salord, A. Delobbe, P. Loubeyre, J-F. Roch
Affiliations : Laboratoire Aimé Cotton, CNRS, Univ. Paris-Sud, ENS Cachan, Université Paris-Saclay, 91405 Orsay Cedex, France ; Laboratoire Aimé Cotton, CNRS, Univ. Paris-Sud, ENS Cachan, Université Paris-Saclay, 91405 Orsay Cedex, France ; CEA, DAM, DIF, F-91297 Arpajon, France ; Orsay Physics S. A., 95 avenue des Monts Auréliens, 13710 Fuveau, France ; Laboratoire Aimé Cotton, CNRS, Univ. Paris-Sud, ENS Cachan, Université Paris-Saclay, 91405 Orsay Cedex, France ; Thales Research & Technology, 1 av. Augustin Fresnel, 91767 Palaiseau Cedex, France ; Orsay Physics S. A., 95 avenue des Monts Auréliens, 13710 Fuveau, France ; Orsay Physics S. A., 95 avenue des Monts Auréliens, 13710 Fuveau, France ; CEA, DAM, DIF, F-91297 Arpajon, France ; Laboratoire Aimé Cotton, CNRS, Univ. Paris-Sud, ENS Cachan, Université Paris-Saclay, 91405 Orsay Cedex, France

Resume : The diamond anvil cell (DAC) is the tool that allows scientists to create pressures comparable to those existing in the Earth core, above the megabar range. These conditions lead to new states of matter with specific magnetic and superconducting properties. However, the minute size of the sample and the constraints associated to the DAC make the implementation of magnetic diagnostics highly challenging. We will report the realization of an optical magnetometry technique that can detect the sample magnetic behavior through the diamond anvil. The sensing is achieved with Nitrogen-Vacancy (NV) centers located at the surface of the diamond anvil, created by nitrogen implantation with a focused ion beam. The NV center has a spin-dependent photoluminescence. By combining a microwave excitation and an optical excitation/readout, we reconstruct the full vectorial magnetic field inside the diamond anvil cell at pressures as high as 30 GPa so far. As a proof-of-principle, we detected the α-ε phase transition of iron with pressure through the monitoring of its magnetization. Preliminary experiments performed on MgB2 demonstrate that a superconducting state can be detected with the Meissner effect.

Authors : Ludovic Mayer, Thierry Debuisschert
Affiliations : Thales Research & Technology, 1 avenue Augustin Fresnel, 91767 Palaiseau, France

Resume : The nitrogen-vacancy (NV) color center in diamond is an atom-like system in the solid-state which specific spin properties can be efficiently used as a sensitive magnetic sensor. An external magnetic field induces a Zeeman shift of the NV center levels which can be measured using Optically Detected Magnetic Resonance (ODMR). The use of an ensemble of NV centers, with four possible orientations, allows measuring the three spatial coordinates of the magnetic field at a given location. Combining a diamond crystal holding a layer of NV centers at its surface and a wide-field microscope that monitors the NV’s luminescence allows measuring the magnetic field produced by a large sample located close to the NV layer. Such a magnetic imager can also be exploited the reverse way to perform spectral analysis in the radiofrequency domain. For that purpose, a controlled magnetic field gradient is applied to the diamond crystal which results in a direct correspondence between the spatial position and the frequency of the electronic spin resonance of the NV centers. The magnetic field gradient is aligned along one of the four possible orientations both to preserve the photophysical properties of the NV centers and to make the bandwidth tuning easier. As a result, we obtain an instantaneous image of the incoming frequency spectrum. Combining a commercial “optical grade” CVD diamond and a standard Nd-magnet, we managed to build a compact spectrum analyzer using NV centers to detect microwave signals ranging from 10 MHz to 18 GHz with a 1 MHz resolution, a 20 dB dynamics and a 1 ms refresh time.

10:30 Coffee Break    
Eectronic Devices : Richard B Jackman
Authors : Masataka Imura, Meiyong Liao, and Yasuo Koide
Affiliations : National Institute for Materials Science (NIMS)

Resume : Single-crystal AlN/diamond heterojunction with high-density interface hole channel was successfully obtained by metal-organic vapor phase epitaxy. AlN layer was epitaxially grown on hydrogen-terminated (H-)diamond(111) substrate. Thermal treatment of diamond substrate was carried out under hydrogen and ammonia mixture environment at 1250 oC just before AlN growth. This thermal treatment led to surface sheet hole density as high as ~1.0 × 10^14 cm^-2 without structural reconstruction of diamond surface. In addition, the use of smaller off-cut angle (0.20 ± 0.25o) H-diamond(111) substrate combined with this treatment enabled to obtain single-crystal epitaxial AlN layer, which simultaneously acted as passivation of the surface hole channel with such a high density. The AlN/H-diamond(111) hetero-junction revealed type-II staggered energy band configuration with valence band offset of ~2.0 eV, which is suitable for the fabrication of p-channel field-effect transistor using AlN-gate-insulator/ diamond heterojunction. These results are promising for the development of AlN/diamond hybrid power electronic devices. In this presentation, the electric and structural properties, microstructure at the interface, and electronic devices will be presented.

Authors : Khaled Driche, Hitoshi Umezawa, Toshiharu Makino, Masahiko Ogura, Hajime Okumura, Etienne Gheeraert
Affiliations : Universite Grenoble Alpes CNRS, Institut NEEL Graduate School of Pure and Applied Science, University of Tsukuba AIST, Advanced Electronics Research Center

Resume : Diamond is a promising candidate material for the next generation of power devices owing to its exceptional properties such as extreme wide bandgap, high breakdown field and high thermal conductivity. The high figures of merit of diamond suggest a potential use of diamond based unipolar devices in high temperature, high frequency and low losses applications. In the present decade, many improvements on crystal growth, doping control, defect reduction and device design were reported [1]. Metal-semiconductor field effect transistors (MESFETs) fabricated on hydrogenated diamond surface showing good current density (>100 and good transconductance values (>40, as well as MESFETs fabricated on oxygenated diamond exhibiting blocking capabilities over 1.5 kV have already been reported [2-3]. Despite the high breakdown voltages (BVs), these obtained values are still far from the expected one. In this work, MESFETs were fabricated by integrating selectively grown heavily doped layer under the Ohmic electrodes to decrease the contact resistances. Molybdenum was used for the Gate Schottky contact. The MESFET exhibited a maximum current density of -0.06 and a specific on-resistance of 4.2 kΩ.cm for the shortest gate length and gate to drain distance. The highest BV ever reported obtained for the longest gate to drain distance (50 μm) and largest gate length (30 μm) was 2288V. Lateral depletion expansion observed by electron beam induced current will also be presented. [1] H. Umezawa, Materials Science Semiconductor Processing, vol. 78 (2018), pp. 147–156. [2] G. Conte et al., Nanotechnology, vol. 23 (2012), p. 025201. [3] H. Umezawa et al., IEEE Electron Device Lett., vol. 35, no. 11 (2014), pp. 1112–1114.

Authors : Marie-Laure Hicks, Alexander C. Pakpour-Tabrizi and Richard B. Jackman
Affiliations : London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH, U.K

Resume : Reactive Ion Etching (RIE) has emerged as a preferred method for diamond substrate surface treatment and device patterning. This process is crucial to achieve the fabrication of high power devices fully exploiting the exceptional properties of diamond. The material properties of diamond however pose challenges to achieving smooth etched surfaces, especially for etch depths beyond 2 microns. Following work optimising Inductive Coupled Plasma RIE etching for surface smoothing and removal of sub-surface damage, an investigation into the effects of etch process parameters on diamond patterning is pursued. The aim is the achievement of deep etching with controlled wall angle, minimized micro-masking and etched surface damage. More specifically, the impact of gas ratio and ICP power settings on the physical and chemical properties of the etch is studied with relation to mesa quality. Results highlight the importance of high platen/ICP power ratio, increased O2/Ar gas ratio and intermittent Ar/Cl2 plasma to reduce damage and micromasking on the etched surface, producing a high quality smooth 8 micron deep etch. Acknowledgements The EU Horizon 2020 project ‘GreenDiamond’ is gratefully acknowledged for financial support, as is the UKs Engineering and Physical Sciences Research Council (EPSRC) for the award of a PhD studentship to M-LH.

Authors : M. Gutiérrez, J. Cañas, M.P. Villar, D. Eon, J. Pernot, D. Leinen, D. Araujo
Affiliations : Dept. Ciencias de los materieles e IM y QI, University of Cadiz, 11510-Puerto Real (Cadiz), Spain Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France Departamento de Física Aplicada, Laboratorio de Materiales y Superficie, Facultad de Ciencias, Universidad de Málaga, E-29071 Málaga, Spain

Resume : The outstanding characteristics of diamond for power electronic devices motivate in the last decade the development of new power devices as Schottky diodes or MOSFETs. Concerning the latter, most of the effort has been dedicated to H-terminated diamond MOS structure which allows to reach relatively good sheet resistance (around 1013cm-2) but is limited in hole mobility (10-200cm-2/Vs) probably due to some surface ionic scattering effects. This does not lead to reach high current in the MOSFET devices. Another approach is to design bulk channels in spite of surface channels. For this purpose -doped channels were investigated in the past but the carrier delocalization has not been reached and thus the hole mobility stays below 10cm-2/Vs. Among the bulk channels approaches, an alternative is the classic metal/oxide/diamond stack, with an oxide-terminated diamond surface, where relatively high carrier mobilities have been recently reached (1000cm-2/Vs). A good control of the alumina crystallinity allows to reduce the leaks, however, to deeply understand the carrier behavior at the gate stack, the band setting at the diamond/alumina interface is necessary. STEM-EELS and XPS investigations allowed to show the importance of the alumina phase and crystallinity. Band setting can be deduced from XPS analysis using a very thin (2-3nm) oxide layer at the surface of the diamond active layer. J. Marechal et al deduced a valence band-offset of 1,34eV but TEM analysis showed that the microstructure was amorphous alumina. Here, new analysis by XPS on other samples allowed to obtain, with a higher accuracy on the C related peak, a reduced value. As interface levels can pin the Fermi level and modify such band setting compared to monocrystalline alumina which is the phase required to eliminate leaks, similar analysis has been performed on monocrystalline alumina. Here, XPS profiling analysis across a 40nm thick alumina layer down to the diamond is reported. XPS spectra obtained by FIB related milling with Ga+ ions are compared to in-situ Ar milling in the XPS. Both approach allowed to deduce a valence band offset of 1,7eV. In addition, STEM-EELS investigations permit to follow up the alumina energy bandgap description at the gate MOSFET stack. In conclusion, crystallographic aspects as the phase, the monocrystallinity and the crystal orientation at the interface are here shown to be of first importance to understand the carrier dynamic at the oxide/diamond interface. For alumina grown by ALD at 380ºC followed by an annealing at 500ºC, monocrystalline -alumina is obtained with a bandgap of 6,8eV and a valence band setting of 1,7eV which is very promising to obtain diamond MOSFETs working in accumulation regime.

Single Crystal Growth and Advanced Devices : Oliver Williams
Authors : Amanda Charris, William Holber, Robert Basnett, Travis Wade, Andrew Basnett, Doug Hansel and Adam Brown
Affiliations : Plasmability LLC, Austin, Texas, United States

Resume : An inductively coupled toroidal plasma source is used as an alternative to microwave plasma for chemical vapor deposition (CVD) of diamond material. The toroidal reactor operates with a 400 kHz power source at up to 11 kW of coupled power. The toroidal system has been configured to create an efficient environment for diamond deposition at high power density (~ 800 W/cm3). The plasma shape is a line source so that it is ideal for the growth of single crystal diamond on multiple seeds places along the line of plasma. Position of the samples is dynamically controlled during the growth process, so that the growth surface can be kept at all times at an optimum distance relative to the plasma core. Plasma-independent temperature control will be discussed. This presentation will cover our work aimed at improving the quality of bulk and epitaxial crystalline diamond material. A wide range of process parameters has been investigated, with the aim of optimizing growth rate, growth quality, and diamond morphology. Work will be described that improves the quality of the bulk diamond material by eliminating growth defects and the polycrystalline material at the edges. Single crystal diamond material is grown on 5 mm x 5 mm and 7 mm x 7 mm CVD (100)-oriented diamond seeds. The linear growth rate for high-quality single crystal diamond was in the range of 30 um/hr to 90 um/hr. This work is carried out in part under support from Army Research Laboratory SBIR Contract W911QX-16-P-0222.

Authors : P. Oliva, M. C. Rossi, S. Salvatori, G. Conte, T. Kononenko, V. Ralchenko, V. Konov
Affiliations : P. Oliva: 1. Department of Sciences, University Roma Tre, Via Vasca Navale 84, 00146 Rome, Italy 2. Niccolò Cusano University, Via Don Carlo Gnocchi 3, 00166 Rome, Italy 3. MIFP, Via Appia Nuova 31, 00040 Marino (Rome), Italy; M. C. Rossi: 4. Department of Electronic Engineering, Universit di Roma Tre, Roma, Italy; S. Salvatori: 2. Niccolò Cusano University, Via Don Carlo Gnocchi 3, 00166 Rome, Italy; G. Conte: 1. Department of Sciences, University Roma Tre, Via Vasca Navale 84, 00146 Rome, Italy 5. Institute for Structure of Matter, CNR-ISM, Via Salaria km 29, Montelibretti, Italy; T. Kononenko: 6. A.M. Prokhorov General Physics Institute, RAS, 38 Vavilova Street, Moscow, Russian Federation; V. Ralchenko: 6. A.M. Prokhorov General Physics Institute, RAS, 38 Vavilova Street, Moscow, Russian Federation 7.National Research Nuclear University mEPhI, Kashirskoye shosse 31, Moscow, Russian Federation; V. Konov: 6. A.M. Prokhorov General Physics Institute, RAS, 38 Vavilova Street, Moscow, Russian Federation 7.National Research Nuclear University mEPhI, Kashirskoye shosse 31, Moscow, Russian Federation;

Resume : The paper reports the study of a detector with graphite pillar contacts, 30 micrometer in diameter, 300 µm in depth, buried within a sc-CVD diamond plate. We used a femtosecond-pulsed IR laser to induce diamond-to-graphite transformation on both the surface and within the bulk volume. Micro- Raman measurements performed in a confocal backscattering geometry and optical microscopy with crossed-axis polarization highlight the presence of stress preferentially developed along (111) directions, laterally each buried pillar. Notwithstanding such stress, the graphite pillars showed good electrical response under high-energy particle incidence, demonstrating to be suitable to collect the charge carriers produced by the energy released inside the bulk volume by ionizing particles. We used electrons and protons to test the generation and charge carriers’ collection efficiency. The collection distance evaluated with MeV energy electrons is about 450 µm while the collection efficiency, evaluated within a “semi-cell” for impinging MeV protons, notwithstanding the apparent stress induced by the laser processing, was as high as 97%. The graphite pillars were not fabricate as “pass-through” columns, but their end is located at about 100 μm away from the bottom surface, which is therefore completely insulating: this unilateral architecture could represent a simple way for the implementation of a 3D stacked volume detector with lateral graphite pads.

Authors : Alexander C Pakpour-Tabrizi1, Mark Reed2 and Richard B. Jackman1
Affiliations : 1London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London (UCL), 17-19 Gordon Street, London WC1H 0AH, UK 2Yale Engineering, Yale University, New Haven, CT 06520, USA

Resume : We report novel nanoscale electrically addressable diamond devices. Based on extremely high-quality boron-doped diamond ∂-layers (∂-BDD), this technology provides an exciting playground for exotic physics and traditional electronic engineering. Lateral Nano-Wires (L-BDD-NW) are defined in very thin heavily boron doped diamond epi layers. In the results reported here, the delta layer is on the surface of a [100] single crystal diamond. Electrical isolation is possible due to the very low defect and high quality ‘intrinsic’ CVD buffer layer grown on the HPHT substrate before the ∂-layer is grown. The resultant nanowires are some 2nm deep and 10-20nm wide. After etching the L-BDD-NW the spatial confinement and electrical properties of the wire can be further engineered using electrostatic side and top gating. We report exceptional current densities indicative of ballistic transport and preliminary results from the first ever fabricated diamond-FinFET type devices; an architecture used in the silicon industry for the next generation of processor chips, but obviously without the extreme transport properties shown here. A range of other exciting and novel device structures which demonstrate emergent quantum phenomena will also be discussed. Fig 1:This figure shows an example of the nanostructures possible. These structures are electrically addressable and active. a) AFM scan of surface Boron delta layer (false colour) Mesa Etched lateral nanowire (L-BDD-NW) structure. b) Close up of L-BDD-NW c) SIMS profile of representative delta layer.

15:30 Coffee Break    
Nano-crystalline Diamond and Applications : Philip John
Authors : Ralph Jennings-Moors and Richard Jackman
Affiliations : London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH, U.K

Resume : The dissolved oxygen content of water is a highly important metric in a variety of fields. Notably in oceanography and the study of climate change, where dissolved oxygen is a marker for the health of the ocean biosphere. Resilient oxygen sensors are required for long term monitoring of the environment, and at a low price point to enable a high spatial resolution of monitoring across the globe. Diamond platinum microelectrodes have been fabricated using simple and scalable techniques for the measurement of dissolved oxygen. A 2 and 3 electrode approach is demonstrated, for maximum flexibility of deployment. The prospects for the commercial development of the these sensors will be reviewed in this paper, which will also illustrate the novel approach used for Pt nano-particle deposition.

Authors : Tae-Gyu Kim1,*, Chi-Hwan Kim2, Yeong-Min Park2 and Mun-Ki Bae2
Affiliations : 1Dept of Nanomechatronic Engineering, Pusan National University, Busan 46241, Korea 2Department of Nano Fusion Technology, Pusan National University, Busan 46241, Korea

Resume : Boron-doped diamond (BDD) thin films are an excellent electrode materials with a large potential window in aqueous solutions and low background current. The wider potential window and lower background currents make BDD material very attractive for electrochemical analysis experiments. Furthermore, BDD exhibits high chemical stability and electrochemical stability, which makes the material suitable for various applications such as bio-electrochemical applications and water disinfection. However, BDD is low in heat resistance and has a large difference in resistivity and diamond quality depending on the content of boron doping. In this study, boron-doped CVD diamond thin films were fabricated by hot filament chemical vapor deposition process. The optimum condition of the boron doping with the lowest resistivity was established and the characteristics of the diamond and the deposition rate were investigated according to the boron content. In addition, the anti - oxidation test was performed on the deposited diamond film to investigate the thermal stability characteristics. In the diamond deposition process, the CH4 / H2 concentration was fixed at 2% and the B2H6 / CH4 concentration was varied from 0.01 to 0.05%, and the boron doped diamond film was deposited for 4 hours. At this time, the temperature of the filament was 1700 °C to 2400 °C, and the substrate temperature was measured at about 850 °C to 950 °C. In addition, the distance between the filament and the substrate is 0.2 to 2 centimeters. The oxidation temperature was experimentally measured at from 600 °C to 850 °C in a box furnace. The oxidation start temperature of the diamond thin film was measured in an atmospheric air condition, and the morphology and weight reduction rate were measured precisely to determine the oxidation resistance respectively. The boron - doped diamond film was compared with the boron-doped diamond film and the crystallinity, deposition rate, resistivity and thermal stability of the diamond film were compared and analyzed. Cyclic voltammetry of boron-doped CVD diamond films was also measured and analyzed.

Authors : William Parfitt and Richard B. Jackman
Affiliations : London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH, U.K

Resume : The need for accurate and compact monitoring of water quality is becoming ever more pressing, both in civil and military applications. The harsh nature of these fluid systems limits the use of conventional sensing technologies; high temperatures and pressures may be encountered, along with damaging radiation levels and a chemically aggressive environment. Due to its unique mechanical resilience, chemical inertness and radiation hardness diamond presents itself as an ideal material for prolonged exposure to these conditions. Diamond can also be boron-doped to form a p-type semiconductor with properties that facilitate unparalleled electrochemical and sensing performance. Two metrics that are key indicators of water quality are pH and dissolved oxygen concentration. This paper presents an integrated sensor capable of measuring both of these on a single, robust device. An ion-sensitive field effect transistor (ISFET) for the measurement of pH; along with an amperometric electrochemical sensor for the dissolved oxygen concentration have been developed on boron-doped nanocrystalline crystalline diamond. Acknowledgments BAE Systems Maritime and the UKs Engineering and Physical Sciences Research Council (EPSRC) are gratefully acknowledged for the award of a ‘CASE’ PhD studentship to WP. BAE Systems are also thanked for financial support for the project.

Authors : Rafael Garcia-Gutierrez1, Pablo Tirado1,3, Jorge Montes-Gutierrez1, Frank Romo-Garcia1, Carlos Perez-Rabago2, Jesus Alcantar-Peña3, and Orlando Auciello3
Affiliations : 1Departamento de Investigación en Física, Universidad de Sonora, Hermosillo, Sonora, 83000, México;2Instituto de Energías Renovables, Universidad Nacional Autónoma de Mexico, Temixco, Morelos, 62580, México;3Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, TX 75080, USA

Resume : The physics and applications of Nanocrystalline Diamond (NCD) films are been investigated due to their unique combination of properties such as high wear resistance, highest hardness relative to any other film, lowest friction coefficient compared with metal and ceramic coatings, chemical inertness, negative electron affinity, low work function, and the high electrical conductivity for boron doped and nitrogen grain boundary incorporated diamond films. The combination of these properties make doped diamond films suitable for many applications like electrodes for water purification, thermionic and field emission devices, and high power electronic devices. This research is focused on understanding the chemical, structural and electrical properties of Nanocristalline diamonds films before and after doping with boron by thermal diffusion. The diamond films were grown by Microwave Plasma Chemical Vapor Deposition technique on Silicon (100) substrates. The boron doped diamond films were characterized by Raman, XRD, XPS, 4-point probe and C-V analysis. Moreover, progress in the Photo-Enhanced Thermionic Emission (PETE) from the Nanocristalline diamond films under solar concentration is provided in this research.

17:00 Break    
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Colour centers and spin coupling applications : Christoph Nebel
Authors : Fedor Jelezko
Affiliations : Institute of Quantum Optics, Ulm University

Resume : Color centers in diamond are promising for wide range of technology applications including quantum information processing quantum communicating and quantum sensing. Most of results obtained so far with nitrogen vacancy (NV) centers are based on optical detection of single NV color centers. In this talk, we will show that photoelectrical detection of NV centers base on spin selective photoionization can provide robust and efficient access to spin state of individual NV centers.

Authors : Viktor Ivady 1), 2), Igor A. Abrikosov 2), 3), and Adam Gali 1), 4)
Affiliations : 1) Wigner Research Centre for Physics, Hungarian Academy of Sciences, PO Box 49, H-1525, Budapest, Hungary; 2) Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden; 3) Materials Modeling and Development Laboratory, National University of Science and Technology `MISIS', 119049 Moscow, Russia; 4) Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary;

Resume : High degree hyperpolarization of arbitrary samples and nuclear magnetic resonance (NMR) agents is of great importance for sensitivity enhanced NMR sensing and imaging measurements for decades. The spin of the NV center in diamond provides a novel, highly controllable source for realizing new protocols for dynamic nuclear polarization (DNP). Protocols use only optical illumination and operate even at room temperature are of highest importance. Here, we discuss the results of recent theoretical simulations [1] on the optically driven dynamic nuclear polarization of NV center in diamond [2]. We underline the requirement and limitations of efficient hyperpolarization of the diamond host and other substances. [1] V. Ivady, Phys. Rev. B 92, 115206 (2015) [2] V. Jacques, Phys. Rev. Lett. 102, 057403 (2009)

Authors : J. Görlitz [1], D. Herrman [1], M. Gandil [1], P. Fuchs [1], T. Iwasaki [2], T. Taniguchi [3], M. Hatano [2], C.Becher [1]
Affiliations : [1] Fachrichtung NT, Universität des Saarlandes, Saarbrücken, Germany; [2] Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8552, Japan; [3] Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan;

Resume : Recent research emphasizes the excellent suitability of solid state emitters like quantum dots or colour centres in diamond for the purpose of quantum information processing. Two colour centres with outstanding properties are the silicon vacancy (SiV) and the nitrogen vacancy (NV) centre. While showing room temperature coherence times of milliseconds, the NV suffers from an emission of only 4% of emitted photons into its zero phonon line (ZPL). The SiV centre however has 80% ZPL emission while achieving millisecond coherence times only at millikelvin temperatures due to phonon-driven decoherence processes. For these reasons there have been ongoing efforts to find a colour centre in diamond with optimized properties. One promising candidate is the tin vacancy (SnV) centre emitting at 620nm and showing a similar fine structure splitting as the SiV centre, consisting of four lines at cryogenic temperatures. However the SnV centre features a much larger ground and excited state splitting of 850GHz respectively 3000GHz, potentially enabling long spin coherence times even at liquid Helium temperatures. We here present spectroscopic investigations on both single SnV centres and SnV ensembles, such as lifetime, polarisation, temperature dependence of linewidth and line shifts, precise determination of Debye-Waller factor and single photon emission properties, paving the way for further investigations of spin coherence times assessing the suitability of the SnV centre as spin qubit.

Authors : Péter Udvarhelyi, Vladyslav O. Shkolnikov, Adam Gali, Guido Burkard, András Pályi
Affiliations : Department of Biological Physics, Loránd Eötvös University, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary; Department of Physics, University of Konstanz, D-78457 Konstanz, Germany; Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary; Department of Physics, University of Konstanz, D-78457 Konstanz, Germany; Department of Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary MTA-BME Exotic Quantum Phases ”Momentum” Research Group, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary

Resume : The interaction of solid-state electronic spins with deformations of their host crystal is an important ingredient in many experiments realizing quantum information processing schemes. Here, we theoretically characterize that interaction for a nitrogen-vacancy (NV) center in diamond. Using the symmetry-allowed Hamiltonian describing the interaction between the ground-state spin-triplet electronic configuration and the local strain, we have numerically calculated the six coupling-strength parameters of the Hamiltonian using density functional theory. Here we derive the symmetry-allowed Hamiltonian and discuss the computational details of calculating spin-strain interaction for paramagnetic point defects. The importance of this interaction is highlighted by the fact that it enables to drive spin transitions, both magnetically allowed and forbidden, via mechanically driven spin resonance. We have also calculated two coupling parameters yet to be experimentally determined, that are in the same order of magnitude as the other spin-stress coupling strengths and could be used for mechanical driving of the magnetically allowed spin transition.

Authors : Gergo Thiering, Adam Gali
Affiliations : Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, POB 49, H-1525, Hungary; Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111, Budapest, Hungary

Resume : Group-IV – Vacancy color centers in diamond are fast emerging quantum bits that can be harnessed in quantum communication and sensor applications. It is an immediate quest to understand their magneto-optical properties, in order to select the appropriate qubits for varying needs of particular quantum applications. We performed a systematic study [1] on the magnetooptical properties of Group-IV – Vacancy color centers, SiV, GeV, SnV and PbV, in diamond by means of cutting-edge ab initio density functional theory calculations. We identified the photostability of these centers that can act as solid state qubits. We developed a novel spin Hamiltonian for these qubits in which the electron angular momentum and spin as well as the phonons are strongly coupled and identified such terms that have not been considered so far but are important in understanding their magneto-optical properties. We solved ab initio this complex problem for the model of these color centers consisting of up to 1000-atom supercells, and were able to reproduce previous experimental data. Furthermore, we identified SnV(-) and PbV(-) qubits with long spin coherence time at cryogenic temperatures where the spin state of PbV(-) can also be thermally initialized at these temperatures. [1] G. Thiering, A. Gali, Phys. Rev. X, accepted (2018). (arXiv:1804.07004)

15:30 Coffee Break    
Field effect electronic devices : Hitoshi Umezawa
Authors : Mohd Syamsul and Hiroshi Kawarada
Affiliations : School of Advanced Science and Engineering, Waseda University, Tokyo 169-8555, Japan

Resume : This talk will be focused on the potential of grown heteroepitaxial diamond as field effect transistor (FET). Heteroepitaxial growth of diamond as an alternative way producing single crystalline films was established since the early 1990s [1-2]. The highly oriented growth shows promising advantages very similar as single crystalline diamond. Over the past century there has been a dramatic increase in performances for single crystalline diamond FET [3]. It may however be noted that uttermost of the studies were attentive on single crystalline diamond as FET and rigorous studies were performed to realize its maximum performances. Nevertheless, the use of heteroepitaxial diamond as FET were very limited. This was the motivation behind the present findings. We explore the full potential of the heteroepitaxial diamond field-effect transistor (FET). Initially, the talk will be the methodology includes the heteroepitaxial diamond growth via microwave plasma chemical vapor deposition (MPCVD) and followed with device fabrications; undoped homoepitaxial growth, source and drain bilayer metallization, hydrogen termination for C-H bonding, two-dimensional hole gas (2DHG) narrow channel formation, passivation layer deposition and gate metallization. Electrical characteristics will be discussed in depth including the current voltages characteristics and breakdown voltages characteristics. These analyses will also contain heteroepitaxial diamond FET as benchmark contrasted with other diamond power devices and wide bandgap devices. Finally, several improvements will be discussed to initiate a significant step towards realization of the potential of widely available heteroepitaxial diamond for use in FET applications. These findings will drive further advancements in diamond-based FET devices because they offer no limitations in terms of device size or availability on a large scale. References: 1. B.R. Stoner, J.T. Glass, ‘Textured diamond growth on (100) β-SiC via microwave plasma chemical vapor deposition ‘.Appl. Phys. Lett. 60 698–700 (1992). 2. H. Kawarada, C. Wild, N. Herres, R. Locher, P. Koidl, H. Nagasawa, ‘Heteroepitaxial growth of highly oriented diamond on cubic silicon carbide’, J. Appl. Phys. 81 3490–3493 (1997). 3. H. Umezawa, “Recent advances in diamond power semiconductor devices,” Mater. Sci. Semicond. Process., vol. 78, no. September 2017, pp. 147–156, 2018.

Authors : Hitoshi Umezawa, Hiroyuki Kawashima, Shinya Ohmagari, Yoshiaki Mokuno, Daisuke Takeuchi
Affiliations : AIST, Institute Neel/CNRS; AIST; AIST; AIST; AIST

Resume : Radiation-hardened semiconductor electronics are highly required for the nuclear plant application, especially after the severe accident of Fukushima Dai-ichi power plant happened in 2011, Japan. Diamond is one of the expected materials for this application because of its strong covalent bond and radiation inertness of carbon itself [1,2]. Large bandgap and barrier height of junction on diamond enable semiconductor devices working at extremely high temperature > 500deg C [3]. In this study, X-ray radiation hardness as well as high temperature stability of diamond devices have been characterized. Two types of diamond devices such as vertical-structured Schottky barrier diodes (vSBDs) and metal-semiconductor field-effect transistors (MESFETs) were fabricated to evaluate X-ray radiation hardness. Diamond vSBDs were fabricated on a lightly boron doped p-type drift layer deposited on a single crystal p+ type diamond substrate (001) by chemical vapor deposition (CVD). Al2O3 was utilized for the field-plate and the passivation layer to protect the surface. Stacked-metal layer (Ti/Mo/Au) was formed on the back side of the substrate as Ohmic contact, and Mo was deposited on the surface as Schottky (anode) contact. For MESFETs, planer structured MESFETs were fabricated on a p- drift layer deposited on the semi-insulating single crystal diamond substrate (001) by CVD. Before deposition of the Ohmic source/drain contacts, p+ layers were selectively grown to decrease the contact resistance on the drift layer. Mo Schottky metal was formed as the gate contact. The X-ray with the dose rate of 22.2kGy/h from Al (Ka = 1.49 keV) was used to evaluate the radiation hardness. Any degradations of the forward characteristics, such as increase of the ideality factor or degradation of Schottky barrier height on diamond vSBD was not confirmed even after 10 MGy of X-ray irradiation. However, the leakage current was slightly increased as increase of X-ray irradiation. The leakage current of vSBD after 10 MGy of X-ray irradiation was at least 2 orders of magnitude higher than that before the irradiation. Consequently, the rectification ratio on forward/reverse current becomes 7 orders of magnitude. On the other hand, the blocking voltage was improved after the irradiation. The degradation of diamond itself was not confirmed by Raman spectroscopy, accordingly, the origin of the leakage current might be due to the adsorbates from the atmosphere during the X-ray irradiation. The semi-resistive adsorbates make the potential distribution on the surface uniform. More than 10% of improvement of blocking voltage was confirmed on all the characterized devices. For the diamond MESFET, the maximum drain current and transconductance were almost constant to the X-ray radiation even after high dose of 10 MGy, however, the increase of the surface leakage current between Schottky gate and Ohmic drain was confirmed. This phenomena is similar to the case of SBD. The on/off ratio was degraded from 4 to 2 orders of magnitude. We have confirmed that the MESFETs work up to 500degC without fatal degradation. This work is partially supported by Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. Reference: [1] P. Bergonzo et al., Phys. Stat. Sol. A 185 (2001) 167. [2] F. Foulon et al., MRS Proc. 487 (1998) 591. [3] K. Ikeda et al., Appl. Phys. Express 2 (2009) 011202.

Authors : Khaled Driche, Hitoshi Umezawa, Toshiharu Makino, Masahiko Ogura, Hajime Okumura, Etienne Gheeraert
Affiliations : Universite Grenoble Alpes CNRS, Institut NEEL Graduate School of Pure and Applied Science, University of Tsukuba AIST, Advanced Electronics Research Center

Resume : The exceptional physical and electrical properties of diamond such as extreme wide bandgap, high breakdown field and high thermal conductivity make diamond a perfect material to be used for the next generation of power electronics. Several investigations and improvements on crystal growth, doping control, defect reduction and device design [1], will allow diamond based devices to be integrated for high temperature, high frequency and low losses applications. Different field effect transistors (FETs) from metal-oxide-semiconductor FETs (MOSFETs) to metal-semiconductor FETs (MESFETs) either focusing on two dimensional hole gas (2DHG) or bulk conduction (O-terminated surface) have been reported [2-3]. Despite the 1.5 kV high breakdown voltage (BV) reported for the MESFET [4], the obtained value is lower compared to the theoretically expected one. The first fabricated Reverse Blocking (RB) MESFETs will be presented. The RB MESFET provides a bi-directional switch that improves the on-state power loss. A Schottky electrode was used for both gate and drain contact. The maximum current was 1 μA. The BV for the normal MESFET was -1.8 kV and over 3 kV for RB MESFET. The fabricated RB MESFET, without any optimization, has blocking capabilities comparable to an optimized 4H-SiC MOSFET [5]. EBIC analysis to understand the low BV will be discussed. [1] H. Umezawa, Mater. Sci. Semicond. Process., vol. 78 (2018), 147–156. [2] G. Conte et al., Nanotechnology, vol. 23 (2012), p. 025201. [3] T.-T. Pham et al., IEEE Electron Device Lett., vol. 38, (2017), 1571–1574. [4] H. Umezawa et al., IEEE Electron Device Lett., vol. 35 (2014), 1112–1114. [5] S. Mori et al., in Proceedings of the International Symposium on Power Semiconductor Devices and ICs, 2016.


No abstract for this day

Symposium organizers
Ádám GALIWigner Research Centre for Physics

Hungarian Academy of Sciences, Konkoly-Thege Miklós út 29-33, Budapest, 1121, Hungary

+36 1 392 2222/1913
Hitoshi UMEZAWAAdvanced Power Electronics Research Center

National Institute of Advanced Industrial Science and Technology (AIST), Midorigaoka 1-8-31, Ikeda, Osaka, 563-8577, Japan

Saclay, 91191 Gif-sur-Yvette, France
Richard B. JACKMANUniversity College London (UCL)

London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, 17-19 Gordon Street, London, UK

+44 791 484 9269