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Deformation of TCO/Si planar structures under concentrated load action


Author: Harea Evghenii
Degree:doctor of physics and mathematics
Speciality: 01.04.10 - Semiconductors physics and engineering
Year:2011
Scientific adviser: Daria Grabco
doctor habilitat, professor, Institute of Applied Physics of the ASM
Institution: Institute of Applied Physics of the ASM
Scientific council: DH 02-01.04.10-27.03.08
Institute of Applied Physics of the ASM

Status

The thesis was presented on the 12 October, 2011
Approved by NCAA on the 11 November, 2011

Abstract

Adobe PDF document0.82 Mb / in romanian

Keywords

planar structures, mechanical properties, nanoindentation, film hardness, complex hardness of film/substrat structures, piezoresistance, anormal solubility, pop-in effect, pop-out effect, size effects

Summary

Thesis structure: The thesis is written in romanian and consists of the Introduction, 4 Chapters, Conclusions, References ( a list of 159 cited works), 123 pages on the main body text, 79 Figures, and 9 Tables.

Field of study of the thesis: Physics of strength and plasticity, mechanical properties of materials.

The aim of research: The thesis deals with the study of the mechanical properties of the ITO/Si and SnO2/Si structures, determination of the mechanisms of the interaction between a film and a substrate under the action of a concentrated load. Special attention is paid to the mechanical properties of a film and of the substrate deformed in the presence of a film. The existing current techniques, such as micro-nanoindentation, dynamic and quasi-static indentation, have been applied in the study of the mechanical properties of planar structures. In addition, certain new techniques have been proposed and used.

Scientific novelty and originality: The selective chemical treatment made it possible to visualize the distribution of mechanical tensions in a film. Besides, dislocation rosettes of a substrate under the action of a concentrated load through a film have been used so as to reveal the direct contribution of a film into the mechanical properties of the structure film/substrate.

The study has also demonstrated the linear dependency of the pop-out effect depth (hpop-out) on the maximum depth of the penetration (hm). It has been found out that the relationships ∆hm/∆hpop-out differ according to Si doping as well as to the type of films deposited on the surface.

The theoretical significance: It was defined the mechanism of interaction between the film and the substrate under the external concentrated load action.

Applicative value of the thesis: Of practical interest is the investigation and explanation of the origin of variations of electrical properties of devices fabricated on the base of the structures metal-semiconductor under the influence of an external mechanical pressure.

Chemical instability resulting from the mechanical instability of the material has been experimentally confirmed. A method has been developed to direct a chemical treatment by introducing a mechanical tension in both bulk crystals and polycrystalline films.

The implementation of the scientific results: The method of directing chemical traetment by introducing a mechanical tension in bulk crystals makes it possible to get spacial structures of a complex form (application for a patent).

The same effect is the base for obtaining spacial structures of ITO films (patented). In addition, an abnormal solubility behavior can be suggested as a method to designate tense regions of the structures of the type film/substrate of a different chemical origin by selecting a suitable solvent. Si plates treated mechanically and chemically and used as substrates for solar cells have demonstrated a rise of efficiency by about 2%.