Tutorial - Thin-film synthesis from the vapor phase: fundamentals of processes, growth evolution, and applications

 

General description:

The tutorial aims at providing an overview of: (i) thin-film vapor-based synthesis techniques, (ii) fundamental atomic-scale processes and phenomena encountered during vapor-based film deposition, (iii) theoretical and computational tools used for thin-film design, and (iv) modern and emerging applications of nanoengineered thin films and coatings. The primary audience of the tutorial is Ph.D. and M.Sc. students working in the field, but also scientists and engineers. Lectures will be given by the organizers of the Symposium “Nano-engineered coatings and thin films: from design to applications” but also by experts in the field, as detailed in the following.
 
 

Schedule and modules:

Date/time Lecture topic Lecturer
Monday, May 27, 2019/9:00-10:00   Physical vapor
  deposition and
  reactive sputtering
  Tomas Kubart
  Uppsala University,
  Sweden.
Monday, May 27, 2019/10:00-11:00

  Chemical vapor
  deposition

  Panos Patsalas
  Thessaloniki University,
  Greece
Monday, May 27, 2019/11:15-12:15   Thin film nucleation
  and growth
  Kostas Sarakinos
  Linköping University,
  Sweden
  Tuesday, May 28, 2019/16:00-17:00     Stress generation
  and evolution during  
  film growth
  Gregory Abadias
  University of Poitiers,
  France
Tuesday, May 28, 2019/17:00-18:00    Optical properties of
  thin films and
  plasmonic materials
  Panos Patsalas
  Thessaloniki University,
  Greece
Tuesday, May 28, 2019/18:00-19:00    Computational tools
  for design of thin
  films
  David Holec
  Montanuniversität Leoben,  
  Austria
 
 

Module description:

1. Physical vapor deposition and reactive sputtering
Physical vapour deposition (PVD) techniques are widely used for synthesis of various thin films from laboratory to industrial scale. This module aims at understanding principles of the different PVD techniques and highlights the relation between the process conditions and properties of the resulting films. Special focus is paid to plasma-based techniques, the effect of plasma chemistry and ion assistance is discussed. To illustrate various physical processes, challenges related to low temperature synthesis of photocatalytic materials, high deposition rate of compounds, and growth of transparent conducting oxides are discussed.
The specific aspects to be covered in this module are:
(i) PVD –definition, vapour generation (evaporation and sputtering), material flux characteristics
(ii) Examples of PVD materials and applications, main challenges for processing
(iii) Plasmas in PVD- plasma chemistry and ion assistance
(iv) Magnetron sputtering
(v) Reactive sputtering
 
2. Chemical vapor deposition
Chemical methods for synthesis of nanoengineered films and coatings, such as chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), and atomic layer deposition (ALD), are in the forefront of the thin film science and technology, due to their potential of accurate control of the film chemistry, process scalability, and cost effectiveness. In this module, an introduction to these techniques will be presented; it will include the basic principles, reactor design considerations, reactor optimization, and the role of kinetics on the film microstructure. A review of the nanoengineered films and coatings grown by these techniques, with emphasis to metal nitrides, will be provided. The formation of multicomponent nitride films and coatings by these techniques will be considered, and the factors that are used to produce nanocomposites or ternary and quaternary nitride alloys will be critically evaluated. Finally, a critical comparison with the corresponding PVD films and coatings in view of the potential industrial applications will conclude the module.
 
3. Thin film nucleation and growth
Thin-film technology is pervasive in many applications, including microelectronics, optics, magnetics, hard and corrosion resistant coatings, micromechanics, etc. Progress in each of these areas depends upon the ability to selectively and controllably deposit thin films (thickness ranging from tens of angstroms to micrometers) with specified physical properties. This, in turn, requires control -- often at the atomic level -- of film microstructure and microchemistry. In this module, the fundamental mechanisms that control vapor condensation, atomic diffusion, island nucleation and growth, island coalescence and coarsening, and continuous film formation will be described briefly discussed. Experimental results and simulation data related to growth in homoepitaxial systems, as well as to growth in polycrystalline weakly-interacting film/substrate systems, will be used as illustrative examples. The effect of energetic bombardment on film microstructural evolution will also be highlighted.
 
4. Stress generation and evolution during film growth
The presence of stress in thin films and functional coatings constitutes a major concern in many technological applications, as excessive residual stress levels can dramatically affect the performance, reliability, and durability of material components and devices. This module will start with a description of residual stress sources in PVD thin films, with focus placed on intrinsic stress. Stress evolutions during film growth and post-deposition treatments will be presented, and the underlying atomistic and microscopic mechanisms will be discussed in the framework of a kinetic model. Experimental methods for measuring stress in thin films will be reviewed, based on recent advances in optical, X-ray diffraction and FIB-based techniques, allowing a depth-sensitive determination, as well as real-time diagnostics. The influence of microstructure (grain size, texture) and deposition process parameters on the stress development in PVD hard coatings will be outlined. The role of energetic species, which are typically present during magnetron sputtering or ion-beam assisted deposition, on the compressive stress build-up will be highlighted. Finally, strategies to control and mitigate stress and stress engineering for specific applications will be proposed.
 
5. Optical properties of thin films and plasmonic materials
Plasmonics has emerged as a dynamic research field that is a direct manifestation of nanoscience, due to the feature sizes of the relevant materials, although their basic theory is classical; as a field it promises radical innovations in biotechnology, in terms of both biosensing and therapeutics, photocatalysis, and telecommunications. Plasmonics are based on nanostrutured conductors. Conductive nitrides have emerged as important candidates for this technology, due to their exceptional stability, despite of some drawbacks. In this module an introduction to the theory of plasmonics will be presented. The optical properties of noble metals, along with other metals and conductive ceramics will be critically reviewed and their potential as plasmonic materials will be cross-evaluated. Based on this comparison, the potential of conductive nitrides as plasmonic materials will unravel and the potential applications, that are specifically tailored for their optical performance, will be proposed. Finally, the techniques for the formation of nitride plasmonic nanostructures following either the top-down approach (such as e-beam lithography) or the bottom-up approach (such as self-assembly growth) will be presented and assessed.
 
6. Computational tools of design of thin films
Without doubt, modelling represents an integral part of materials science. It can be used for proving experimental hypotheses, to provide insights beyond the experimental capabilities (resolution in space and time, separating various effects etc.) Importantly, it has now reached stage where modelling can be effectively used to guide experiments. In this module, we will review various techniques spanning from continuum mechanics and classical thermodynamics, over mesoscale techniques such as discrete dislocation dynamics and atomistic approaches, i.e., Monte Carlo and molecular dynamics, to quantum mechanical ab initio methods based on Density Functional Theory. For each technique we will discuss its principles, typical applications (with a special focus on thin films), advantages and shortcomings. We will also stress the need for constant cross-checking with experiments to validate the predictions, but also to steer the modelling efforts, hence leading to "experiment-guided theory".
 
 

Lecturers:

Gregory Abadias is Professor at the Physics Department of the University of Poitiers, France. He received his Ph.D. degree in materials science in 1998 at National Polytechnic Institute of Grenoble (INPG), and he is currently group leader of thin films activities at CNRS Pprime Institute in Poitiers. He conducts research on a range of topics related to nanoscale thin films, including mechanical, electrical and optical properties of metallic, nitride or oxide systems, as well as hard and protective coatings in the form of nanocomposites or multilayers. His current research interests focus on the understanding of thin film growth dynamics using real-time and in situ diagnostics, with main emphasis on the stress development during sputter-deposition of polycrystalline and epitaxial layers. He has co-authored more than 130 peer-reviewed papers and serves as Editor of Surface and Coatings Technology journal since 2016. 
 
David Holec is a group leader of Computational Materials Science at the Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben. David has received his BSc (mathematics, 2002, and physics, 2004) and MSc (condensed matter physics, 2005) degrees from Masaryk University, Brno, Czech Republic, and a PhD (materials science, 2008) from Cambridge University, UK. He has been at the Montanuniversität Leoben since 2008, when he was first appointed as a post-doc. Since 2013 he is also a guest researcher at TU Wien. His strong expertise includes DFT modelling of alloying trends in nitrides and oxides, in addition to other material classes, e.g., novel semiconductors, intermetallics, shape memory materials, and carbon nanostructures. He has published over 100 peer-reviewed papers and has presented 12 invited talks at international conferences. He has supervised a number of BSc, MSc, and PhD students. He teaches several courses on materials modelling and solid-state physics.
 
Tomas Kubart is Associate Professor at the Department of Solid State Electronics at Uppsala University. Tomas is focusing on highly ionized deposition techniques and novel techniques for high quality thin films, especially oxides, for electronics and energy applications. He leads the Thin Films group and is responsible for the Thin Film Deposition area at the Ångström Microstructural Laboratory.
 
Panos Patsalas is Professor of Advanced Materials at the Department of Physics of Aristotle University of Thessaloniki, Greece. He received his B.Sc. in Physics and Ph.D. in Solid State Physics in 1996 and 2001, from University of Ioannina and Aristotle University, respectively. His research interests include the growth of films and nanostructures by vapor techniques, their structural characterization via X-Ray and neutron methods, the surface science, spectroscopy and the optical properties of thin films and nanostructures, and the fabrication of electronic, photonic and plasmonic devices. He is engaged with the research on conductive nitrides for over 20 years. His current research interests focus on the implementation of conductive nitrides in photonic and plasmonic devices. He authored or co-authored more than 150 peer-reviewed papers and has served as Guest Editor of numerous volumes of Elsevier journals.
 
Kostas Sarakinos is Associate Professor at the Department of Physics, Chemistry and Biology at Linköping University and he is heading the Nanoscale Engineering Research Division. He holds a Ph.D. degree in Physics from RWTH Aachen University, Germany (2008) and a Habilitation degree in Materials Science from Linköping University, Sweden (2012). Kostas’s research interests include atomistic processes during film nucleation and growth, growth manipulation, in situ growth monitoring, and deterministic and stochastic film growth simulations. He has co-authored 50 papers and 4 book chapters, and he has presented 15 invited talks at international conferences and schools. He teaches courses related to thin-film physics at both undergraduate and post-graduate level.