Abstract

Dr. Ludvik Martinu
Department of Engineering Physics
Ecole Polytechnique, Montreal, Quebec, Canada

"From understanding plasma-surface interactions to advanced applications functional coatings "

Monday April 7, 2008
4:00 - 5:00 pm
WIL Room 101
Please join us beforehand for refreshments

ABSTRACT:

Recent advances in science and technology stimulate the development of new coating materials, surface and interface engineering processes and thin film systems that provide an ever increasing performance in numerous areas ranging from optics and optoelectronics to aerospace, automotive, biomedical, microelectronic, and other applications. Many successful solutions in these particular fields have been identified when using ion-assisted deposition of thin films and thin film systems with tailored functional characteristics including the complex refractive index, the mechanical and tribological properties such as stress, hardness, friction coefficient and wear, the electrical conductivity, the gas and vapour permeation, and many others.

In this presentation, we will describe our recent studies of the ion-surface interactions in a plasma environment (biased-controlled PECVD and PVD techniques) using a methodology combining in situ real-time spectroscopic ellipsometry (RTSE), dynamic Monte-Carlo simulations, and different complementary microstructural and chemical analysis methods. These have the capability to detect and simulate subplantation-related processes, such as sub-surface structural and compositional modifications, and interface broadening, on time and depth scales relevant to functional coatings deposition. Specifically, we will discuss ion-induced effects resulting in rapid structural and compositional changes below film or substrate surfaces, as well as significant ion mixing and interface broadening, and relocation of a large proportion of deposited atoms below the growth surface.

Following a description of the principal physical processes, we will show examples when the above-mentioned methodology helped to enhance our understanding of the film growth and interface evolution for numerous single and multilayer functional coatings. This includes TiO 2, SiO 2, Si 3N 4, ITO and the nanocomposite superhard TiN/SiN and TiCN/SiCN systems suitable for numerous advanced technological applications.

Of particular interest is the extended plasticity that occurs as a result of stress-induced discontinuous grain growth. Efforts to model this growth with traditional driving forces have proven less than satisfactory, and the importance of grain boundary pinning and the role of stress assisted grain boundary migration appear to be more important. The significance of this finding with respect to the reliability of thin film nanocrystalline devices cannot be ignored, as the mechanical behavior of these structures appears to not only be different than that of microcrystalline metals but dynamic as well.

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