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2015 Spring

Materials for Optics and Optoelectronics

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Advances in the prediction, design, fabrication and characterization of 2-dimensional crystal and metamaterial nanostructures for nanophotonics

This symposium will present novel methods for predicting, designing, fabricating and characterizing 2-dimensional crystal and metamaterials.

 

Scope:

 

2015 has been declared the UNESCO Year of Light, which is provident, since light is being used in newer ways than ever before. Using metamaterials, the diffractive limit of the photon is now being broken through coupling to electrons and phonons. These exciting developments, coupled with the discovery of 2-dimensional materials such as van der Waals crystals, presents unique opportunities and challenges to explore negative-index materials, super-resolution imaging, surface plasmons, and related phenomena in surface phonon polaritons within polar dielectric crystals. The combination of plasmonics with 2-D materials such as graphene has opened exciting new research opportunities.

In order to investigate such structures, and ultimately to put them to practical use, it is necessary to predict, design, fabricate and interrogate structures that over a broad range of length scales, from the single-atom thick and couple nm wide graphene nanoribbons, to the <200 nm plasmonic nanoparticles to metamaterials architectures on the micron-scale using similar methodologies. The merging of multiple length scales must employ novel techniques for fabricating such structures. This symposium will focus on the following aspects associated with researching these materials and their corresponding optical phenomena:

  • Theoretical: Novel analytical, computational and finite-element modeling of structure-property relationships in the optical properties of metamaterials and 2-D crystals.
  • Design and Fabrication: Custom integration of multiple techniques such as ALD, self-assembly, novel instrumentation, top-down and bottom-up assembly. This includes new lithographic techniques, such as helium ion beam milling, dip pen lithography, etc.Design and Fabrication: Custom integration of multiple techniques such as ALD, self-assembly, novel instrumentation, top-down and bottom-up assembly. This includes new lithographic techniques, such as helium ion beam milling, dip pen lithography, etc.
  • Characterization: Novel microscopy techniques from the atomic (TEM) to both near- (e.g. SNOM) and far-field (Raman, FTIR, etc.)

 

Hot topics to be covered by the symposium:

 

  • Van Der Waals Crystals
  • Theory, Fabrication, Design and Characterization of Metamaterials
  • Plasmonics
  • Metamaterials
  • Phonon-Polaritons

 

List of invited speakers:

 

  • Henri Lezec, National Institute of Standards and Technology, Gaithersburg, MD, USA
  • Joshua Caldwell, Naval Research Laboratory, USA – Hyperbolic Metamaterials
  • Doug Werner, Penn State University, USA - Transformation optics design
  • Andrea Alu, University of Texas, USA – Metamaterial design and novel calculations
  • Haltice Altug, ETH, Switzerland – Plasmonic structures for sensing
  • Gianluigi Botton, McMaster University, Canada – EELS Measurements of Metamaterials Structures
  • Mark Lundeberg, IFCO, Spain
  • Zee Hwan Kim, Seoul National University, Korea
  • Rainer Hillenbrand, CIC nanoGUNE Consolider, Spain
Start atSubject View AllNum.
11:15
Authors : Krishna P. Dhakal,1,2 Shrawan Roy,1,2 Yun Seok Joon1,3, Ki Kang Kim, Young Hee Lee1,2 and Jeongyong Kim1,2*
Affiliations : 1Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Republic of Korea 2Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea 3Department of Energy and Materials Engineering Dongguk University-Seoul, Seoul 100-715, Republic of Korea

Resume : We performed a nanoscale confocal absorption spectral imaging of the intrinsic and chemically doped MoS2 and WS2 to obtain the full absorption spectra in the range 1.5- 3.2 eV with correlated photoluminescence (PL) and Raman analysis. Two chemicals, reduced viologen (BV) and polymer TFSA ((CF(3)SO(2))(2)NH) were used for the n-type and p-type doping effect of the MoS2 and WS2 monolayer films by drop casting method. Our observations demonstrated the adsorption of the chemicals on 2D materials surface withdraw or transfer electron and modulates light emission between neutral exciton and trion in the PL spectra and modify the optical absorption spectra. We observed the enhancement of A exciton absorption peak with blue shift in peak position for p type doped WS2 monolayer. This could be due to splitting of the trion and favored the transition of direct neutral exciton with less chance of pauli blocking effect as the Fermi level shifts towards the valence band. This increase in band edge absorption explains the drastically enhanced PL property. On the contrary, n doping showed the quenching and red shifting of the band edge exciton of MoS2 while WS2 has shown largely red shifting exciton peak rather than quenching. This effect is attributed to the combined effect of Pauli blocking and screening effect as the Fermi level shifts towards the conduction band. Poor exciton quenching in WS2 may be caused by low level of electron doping compared to MoS2 and require further analysis.

L.L1.6
11:30
Authors : C. Brodehl, T. Riedl, S. Greulich-Weber, J. K. N. Lindner
Affiliations : University of Paderborn, Warburger Str. 100, 33098 Paderborn, Germany CeOPP - Center for Optoelectronics and Photonics Paderborn

Resume : Metasurfaces can show unique properties and can be designed e.g. as flat lenses by using well-shaped metallic nanoparticles. Nanosphere lithography (NSL) is one possibility to produce such tailored nanoparticles on large scale. Thereby, a self-assembled hexagonally closed packed mono- or bilayer of nanospheres covers a substrate and acts in a following metal evaporation process as a shadow mask. There, material is evaporated onto the substrate through mask openings formed by sphere triples. The three-dimensional (3D) morphology of the obtained triangular shaped nanoparticles determines their plasmon resonance and depends on the hole mask itself (arrangement, diameter of spheres, etc.) and the time-dependent modification of the holes during the evaporation process. With ongoing evaporation, material is deposited not only on the substrate, but also on top of the mask itself. Therefore, the mask openings become smaller and more round shaped. This change of the mask openings affects directly the shape of the obtained Au nanoparticles. Their morphology was analyzed by means of energy filtered transmission electron microscopy (EFTEM) thickness maps. By comparison of the found thickness distributions of the Au nanoparticles with those computed by a ray-trace type algorithm the clogging rate of the mask openings is deduced. This procedure allows to predict the morphology of NSL nanoparticles correctly, as long as preferential growth along low-index crystal directions is neglected.

L.L1.7
 
Hyperbolic and Plasmonic Metamaterials : Andrea Alu, Thomas Taubner
13:30
Authors : Wenqi Zhu,1,2, Ting Xu, 1,2, Amit Agrawal, 1,2 and Henri J. Lezec ,1
Affiliations : 1Center for Nanoscale Science and Technology, National Institute of Standards and Technology Gaithersburg, MD, USA; 2 Maryland Nanocenter, University of Maryland, College Park, MD, USA

Resume : Hyperbolic metamaterials, a class of artificially engineered materials with a highly anisotropic permittivity response originating from opposite signs of the principal components of the electric tensor, have attracted significant interest in recent years due to their ability to manipulate the propagation light in exotic ways. Such materials enable distinctive optical phenomena such as negative refraction, super-resolution imaging, and enhanced spontaneous emission. Here we exploit the hyperbolic iso-frequency characteristic of a planar type-II HMM (composed of a template-stripped stack of alternating, 25-nm-thick, sputtered films of Ag and SiO2) to achieve high-sensitivity proximity detection of nanoparticles in transmission. The iso-frequency surface of the HMM is unique in that propagation of light over the entire visible-range is allowed only for electromagnetic modes having tangential spatial frequencies kx exceeding the free-space wavevector k0 by over a factor of two [1]. Due to its high sensitivity to nanoparticles in deep-subwavelength proximity to a surface, achieved without the use of dark-field optics, this HMM-based device hints at promising applications in bio-chemical sensing, particle tracking and contamination analysis. Template-stripped refractive-index-change sensors consisting of ultra-high quality factor open-cavity resonators for surface-plasmon polaritons will also be discussed. 1. T. Xu & H.J. Lezec, Nat. Comm. 5, 4141 (2014).

L.L2.1
14:00
Authors : B. Brudieu 1, 2, J. Teisseire 1, I. Gozhyk 1, A. Le Bris 1, 3, F. Guillemot 4, G. Dantelle 2, F. Sorin 3, T. Gacoin 2
Affiliations : 1 Laboratoire de Surface du Verre et Interfaces, Unité mixte de Saint-Gobain – UMR 125, France 2 Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, France 3 Institut des Matériaux, Ecole Polytechnique Fédérale de Lausanne, Suisse 4 Produits Composites et Revêtements de Surface, Saint-Gobain Recherche, France

Resume : The light management becomes the key-point for photoactive material like solar cells or OLED. The optimization of photonic and optoelectronic systems with engineered dielectric structures provide a promising versatile solution. In this contribution, we demonstrate highly efficient and tunable light trapping structures prepared using simple and scalable Sol-Gel chemistry, wet coating processing, and Nanoimprint techniques. Defect-free Distributed Bragg Reflectors are obtained through combination of the materials with high (dense TiO2 layers, n=2.08 in the visible range) and low refractive index (macroporous silica layers, n=1.24 with 50% of porosity) in the periodic dielectric stack. Such high index contrast allows for specular reflectivity of up to 96% at the normal incidence for as little as 9 layers in the stack. Apart from its simplicity, proposed technique has a high potential for industrial deployment, as the porous layers are prepared thanks to a porogen latex that is calcinated during a single annealing step of the full stack. We also demonstrate the flexibility of our process by making highly reflective DBRs with a tunable reflection range from UV to IR (from 400nm to 1300nm). A prove of concept has been obtained by increasing the efficiency of a-Si:H thin-film solar cell while containing our optimized 8-layer DBR. Moreover, we will show how the integration of diffraction gratings fabricated by Nanoimprint into our DBR structures improves their efficiency.

L.L2.2
14:15
Authors : M.E. Nasir, S. Peruch, N. Vasilantonakis, W.P. Wardley, W. Dickson, G.A. Wurtz, and A. V. Zayats
Affiliations : Department of Physics, King’s College London, Strand, London WC2R 2LS, UK

Resume : Plasmonic nanorod metamaterials display extremely high sensitivity to the surrounding refractive index, and have already been employed as ultrasensitive bio-, ultrasound and hydrogen sensors. They may exhibit hyperbolic dispersion and a spectrally tunable epsilon near zero (ENZ) frequency. Typically, metamaterials comprised of arrays of free standing metallic nanorods are synthesised from porous alumina template obtained using conventional electrolytes such as sulphuric acid and oxalic acid and have an ENZ wavelength which is limited to the visible spectral range 530-650 nm. In order to provide ENZ-related functionalities in the infrared, including at telecom wavelengths, a new approach is needed. Here we describe the design and fabrication of periodic arrays of free standing Au nanorods which allows the ENZ frequency of a nanorod metamaterial to be tuned from the visible to infra-red region using porous alumina templates obtained using Selenic acid. Perfectly ordered nanoporous alumina templates with ~15 nm pore diameter and ~125 nm interpore spacing, having large domain areas, are fabricated by employing two-step anodization in Selenic acid. The ENZ frequency is then tuned by controlling the nanorod diameter via post processing of the pores while keeping the inter-rod spacing and length constant. These metamaterials open up new possibilities for a variety of applications in the fields of bio- and chemical sensing and nonlinearity enhancement in the infrared.

L.L2.3
16:15
Authors : Aliaksandra Rakovich, Pablo Albella, Stefan A. Maier
Affiliations : Imperial College London

Resume : Parallel fabrication of nano-sized sources is one of the major challenges facing nanophotonics today. During the past decade, plasmonics have demonstrated excellent potential in their ability to confine and process optical signals on nano-scale dimensions. In recent years, research in plasmonics-based nanophotonics has been extended to include the interaction of plasmonic structures with active materials, such as fluorescent media, with the aim of developing functional nano-scale optical components. The application of this research to the development of plasmonics-based sources has, however, been hindered by the limitations imposed by the properties of the fluorescent materials in high electric fields, such as those typically produced by dimer nanoantennas. Alternate geometries of plasmonic structures, such as Plasmonic Ring Cavities, offer several advantages despite the reduced electric field enhancements. In particular, the large hotspot sizes of these structures allow coupling of the collective emission of a large number of colloidal semiconductor quantum dots (QDs), selectively placed in their vicinity. In this coupled system, the radiative behaviour of the QDs is altered deterministically, i.e. it can be predicted theoretically given the dimensions of the plasmonic structure and the separation of the fluorescent and plasmonic components. These results have great implications for the scalable and parallel fabrication of plasmonic sources, with the promise of the manufacturing of devices to exact specifications.

L.L2.8
16:45
Authors : Yoku Tanaka1, Keisuke Takano1, Abdallah Chahadih2, Abbas Ghaddar2, Xiang-Lei Han2, François Vaurette2, Willie J. Padilla3, Tahsin Akalin2, and Masanori Hangyo1
Affiliations : 1 Institute of Laser Engineering, Osaka University, Osaka, Japan 2 Institute of Electronics, Microelectronics and Nanotechnology (IEMN), Lille 1 University, France 3 Boston College, USA

Resume : Planar metamaterials or metasurfaces show rich electromagnetic transmission properties depending on their structures. The electromagnetic transmission spectra of metallic checkerboard pattern show drastic change whether the metal squares touch each other (inductive) or not (capacitive). If we introduce the randomness in the connection of the squares or the small finite resistivity areas in the connecting parts, the transmission spectra become flat in frequency dependence. In this communication, we investigate how the spectra and their polarization dependence are modified by adding elements in the opening areas and/or making holes in the metal squares in order to obtain guidelines for designing necessary filters. Additional elements offer new degrees of freedom in the control of THz waves. During the conference, we will present the results with different additional elements and illustrate them with simulations and explain the transmission mechanisms.

L.L2.10
Start atSubject View AllNum.
16:00
Authors : F. Ruffino, M. G. Grimaldi
Affiliations : F. Ruffino, M. G. Grimaldi Dipartimento di Fisica e Astronomia Università di Catania, via S. Sofia 64, 95123 Catania, Italy MATIS CNR-IMM via S. Sofia 64, 95123 Catania, Italy

Resume : Surface nano-patterns of noble metals films are widely studied for nano-electronics, plasmonics, and sensing applications. The spatial arrangement of the surface nano-patterns is of prime importance in tuning the physical and chemical properties of such systems. Therefore, the fabrication of surface nano-patterns with different arrangements is highly desired. Even if various lithography methods are powerful approaches to prepare metallic nanoscale patterns on surfaces, those based on template-confined films dewetting are attractive because of low cost, high throughput, and versatility in fabricating surface nano-structures. In this work, we report about an experimental proof-of-concept of the fact that a controlled variation of the film thickness in the same sample can lead to patterned arrays of metal nanoparticles (NPs) with long-range multimodal size distributions and controlled spatial organization. In particular, by template-confined depositions, Au and Ag micrometric squares of symmetric or asymmetric trapezoidal cross-section profile (i. e. variable thickness) on SiO2 surface were produced. After the thermal-induced dewetting process of the squared patterned Au and Ag films, two-dimensional arrays of multimodal size distributions of Au or Ag NPs were obtained arranged in specific spatial organizations dictated by the starting films patterns. Microscopic analyses allowed us to correlate the mean size and spacing of the NPs with the thickness of the deposited films.

L.LP4.2
16:00
Authors : H. Zaâri, M. Tadout, O. Mounkachi, A. Benyoussef, M. Benaissa*
Affiliations : Laboratoire LMPHE, Dépt. Physique, Faculté des Sciences, Université Mohammed V, Rabat, Morocco

Resume : First principles calculations were performed to study the electronic structures of gallium nitride (GaN) and aluminum nitride (AlN) nanosheets in order to understand the influence of sheet stacking (in terms of thickness) on structural and electronic properties, as well as the relative stabilities of fully and partially hydrogenated nitride nanosheets. Unlike bare GaN and AlN nanosheets terminating with polar {0001} surfaces, their hydrogenated counterparts preserve the initial wurtzite configuration. Specifically, the dielectric function, absorption coefficient, optical conductivity, extinction index, reflectivity and their fraction index of both type of nanosheets are calculated for both parallel and perpendicular electric field polarizations. The results show that the optical spectra are isotropic along these two polarizations. Optical conductivity in both the parallel and the perpendicular electric field starts with an indirect gap (instead of indirect gap for bulk counterparts) which confirms that nitride nanosheets have a semiconductor property.

L.LP4.3
16:00
Authors : Guru P. Neupane,1,2 Krishna P. Dhakal,1,2 Shrawan Roy,1,2 Hyun Kim,1,2 Jubok Lee,1,2 Min Su Kim,1 Ganghee Han,1 Young Hee Lee1,2, Jeongyong Kim1,2*
Affiliations : 1Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Korea 2Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea

Resume : We report the controllable nanosize local thinning of bi- and few layer thicknesses molybdenum disulfide (MoS2) films down to the monolayer thickness by simple method of annealing in dry oxygen atmosphere. The annealing temperature was optimized in the range of 240 to 270 degree centigrade for 1.5 hours and monolayer thickness nanosize pits were developed on the uniform film of the bi- and few layer MoS2 grown by chemical vapor deposition method. We have characterized the formation of nano size pits by nanoscale confocal photoluminescence and Raman spectroscopic imaging technique. We found that PL intensity increased and the Raman frequency shifted showing the characteristics of monolayer MoS2 films, which are believed to be originated from the formation of nanosize monolayer pits on the multilayer thicknesses MoS2 films due to the etching process started at the certain defect sites of the MoS2 in the presence of the oxygen at high temperature .

L.LP4.4
16:00
Authors : Guru P. Neupane,1,2 Krishna P. Dhakal,1,2 Shrawan Roy,1,2 Hyun Kim,1,2 Jubok Lee,1,2 Min Su Kim,1 Ganghee Han,1 Young Hee Lee1,2, Jeongyong Kim1,2*
Affiliations : 1Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Korea 2Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea

Resume : We report the controllable nanosize local thinning of bi- and few layer thicknesses molybdenum disulfide (MoS2) films down to the monolayer thickness by simple method of annealing in dry oxygen atmosphere. The annealing temperature was optimized in the range of 240 to 270 degree centigrade for 1.5 hours and monolayer thickness nanosize pits were developed on the uniform film of the bi- and few layer MoS2 grown by chemical vapor deposition method. We have characterized the formation of nano size pits by nanoscale confocal photoluminescence and Raman spectroscopic imaging technique. We found that PL intensity increased and the Raman frequency shifted showing the characteristics of monolayer MoS2 films, which are believed to be originated from the formation of nanosize monolayer pits on the multilayer thicknesses MoS2 films due to the etching process started at the certain defect sites of the MoS2 in the presence of the oxygen at high temperature .

L.LP4.6
16:00
Authors : Shrawan Roy,1,2 Krishna P. Dhakal,1,2 Guru P. Neupane,1,2 Jubok Lee,1,2 Changwon Seo,1,2 Min Su Kim,1 Ganghee Han,1 and Young Hee Lee,1,2 Jeongyong Kim1,2*
Affiliations : 1Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Korea 2Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea

Resume : Monolayer Molybdenum disulphide (MoS2) is a two dimensional dichalcogenide material, exhibiting direct band gap transition and intensively investigated for many optoelectronic applications [1]. Zinc oxide (ZnO) is a wide band gap semiconductor material which possesses various applications in the optoelectronics devisees. Recently, vertically coupled ZnO nanorods on the surface of monolayer MoS2 demonstrate the enhance photoluminescence of MoS2 monolayer due to light antenna effect [2]. However, many optoelectronic property studies of the different kinds of ZnO/MoS2 nano systems are not investigated yet. In this work, we demonstrated the epitaxial growth of ZnO nanoparticles using simple solvothermal method on the surface of the monolayers MoS2 grown by chemical vapor deposition (CVD) method. Higher particle density was observed on the surface of MoS2 monolayer than on the SiO2/Si substrate as seen in the scanning electron microscopy (SEM) image. We also studied the photoluminescence (PL) spectra of this hybrid system in which PL of ZnO NPs was reduced on the MoS2 surface which could be an indication of the charge transfer from ZnO NPs to the MoS2, will be presented. 1. Krishna et al. Nanoscale 2014, 6, 13028-13035. 2. Zhang et al. Nano Res. DOI: 10.1007/s12274-014-0557-1.

L.LP4.7
16:00
Authors : A.Soltani, F.Ouerghi, F.AbdelMalek and H.Bouchriha
Affiliations : Laboratoire des Matériaux Avancées et Phénomènes Quantiques, Département de Physique, Faculté des Sciences de Tunis, Université de Tunis El Manar, Campus Universitaire, 2092 Tunis, Tunisia.

Resume : The optical diode is in analogy with semiconductor diode that passes electricity from one side only. In two-dimensional (2D) photonic crystals (PC’s), we demonstrate the compact optical isolator in which light can propagate only one way. We propose the design of an optical diode based on the two dimensional square-lattice photonic crystal with the circular defects. Owing to the modes’ match and mismatch between the defect and the adjacent waveguides, the unidirectional propagation of the fundamental mode light beam resonant at a certain frequency is obtained. The transmission coefficient of light depends on the propagation direction and no reciprocal transport of light can happen in the nanostructure. In addition, by using the FDTD method, the electromagnetic fields distributions of the forward and the backward directions are shown.

L.LP4.9

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Symposium organizers
Nabil BassimMaterials Research Engineer - U.S. Naval Research Laboratory

Code 6366 4555 Overlook Avenue, SW Washington, DC

+1 11 202 767 2007
nabil.bassim@nrl.navy.mil
Frank KoppensICFO- The Institute of Photonic Sciences - Mediterranean Technology Park

Av. Carl Friedrich Gauss 3 08860 Castelldefels (Barcelona) Spain

+34 93 553 41 63
+34 93 553 40 00
frank.koppens@icfo.es
Stefan MaierDepartment of Physics - Imperial College, London

Huxley 903 London SW7 2AZ UK

+44 (0)20 759 46063
+44 (0)20 759 42077
s.maier@imperial.ac.uk
Thomas TaubnerPhysikalisches Institut

RWTH Aachen 52056 Aachen Germany

+49 (0)241-80-20260
taubner@physik.rwth-aachen.de