Deformation of TCO/Si planar structures under concentrated load action
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StatusThe thesis was presented on the 12 October, 2011Approved by NCAA on the 11 November, 2011 Abstract – 0.82 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 effectsSummary
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%.
Oficial Reviewers
- Teodor Şişianu
doctor habilitat, professor - Boroica Lucica
dr.,inginer, cerc.şt.principal gr. I, INFLPR, Bucureşti, România
Council's Members
- Leonid Culiuc, president
doctor habilitat, professor, Institute of Applied Physics of the - Veaceslav Ursachi, secretary
doctor habilitat, associate professor (docent), Institute of Applied Physics of the - Alexei Simaşchevici , member
doctor habilitat, professor - Valerian Dorogan, member
doctor habilitat, professor, Technical University of Moldova - Maria Dântu, member
doctor
Theses
