Phase transitions and deformation aspects of Si depending on the loading conditions at the micro- and nanoscale
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StatusThe thesis was presented on the 3 September, 2021Approved by NCAA on the 22 December, 2021 Abstract – 2.78 Mb / in romanianThesisCZU 538.9:538.911:538.951
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Keywords
nanoindentation, hardness, creep, pop-out, elbow, kink pop-out, scratching, deformation mechanisms, scratching speed, AFM, Raman spectroscopySummary
Summary Prisăcaru Andrian „Phase transitions and deformation aspects of Si depending on the loading conditions at the micro- and nanoscale” Thesis for scientific degree of Doctor in Physical Sciences, Chisinau, 2021.
The thesis is written in Romanian language and consists of an introduction, 4 chapters, general conclusions and a bibliography of 152 titles. It contains 137 basic text pages, 68 figures, 7 tables and 27 formulas. The results are published in 14 scientific papers (6 articles and 8 abstracts at international scientific conferences).
Key words: nanoindentation, hardness, creep, pop-out, elbow, kink pop-out, scratching, deformation mechanisms, scratching speed, AFM, Raman spectroscopy.
The goal of the thesis is to study the peculiarities of deformation and phase transitions at nanoindentation, microindentation and nanoscratching of the Si(100) depending on the deformation conditions: long holding time under the load, load value, deformation speed and indenter orientation.
Research objectives: Study of the influence of long holding under the load on the phase transitions, creep development and material deformation/relaxation processes under Si(100) nanoindentation. Revealing of the main deformation mechanisms during Si(100) nanoscratching depending on the scratching speed, load value and indenter orientation.
Scientific novelty and originality of the results: For the first time it has been demonstrated that long holding under the load under Si(100) nanoindentation at room temperature leads to the material creep, formation and expansion of the high pressure α-Si bands in the dislocation zone and extension of Si-III/Si-XII phases, which causes certain effects on the deformation curves. These phases have lower resistivity compared to Si-I and involve the modification of the electrical parameters of Si in the region of residual indentations. Also, for the first time, the evolution and relative contribution of the deformation mechanisms (brittle fracture, plastic flow and ductile cutting) in the scratching process, depending on the speed, load and indenter orientation were determined and the specific influence of these mechanisms on the scratch hardness of silicon was demonstrated.
The main scientific problem solved: The main deformation/relaxation mechanisms, including Si phase transitions, under concentrated load action at the microscale and nanoscale for special conditions - holding under the load and scratching, have been established, which will lead to a deeper understanding of the processes that take place in the real conditions during manufacture and functioning of the Si based micro- and nanodevices. Theoretical significance and applicative value. The influence of the each factor of the deformation conditions (speed, load, holding under the load and indenter orientation), separately and in combination, on the deformation particularities and phase transitions of Si at microindentation, nanoindentation, microscratching and nanoscratching was determined. These results are important for the development of new fast and efficient possibilities for creation of various microsystems, nanosystems, microstructures and nanostructures for micro and mechanical, optoelectronic and biomedical engineering, as well as for their sustainable functioning. The implementation of the scientific results. The obtained results can be used for fast ultra-fine mechanical and mechano-chemical texturing of the Si surface with potential applications in photovoltaic (solar cells), biomedicine (microfluidic and nanofluidic devices), MEMS, etc.
Oficial Reviewers
- Veaceslav Ursachi
doctor habilitat, associate professor (docent), Institute of Applied Physics of the - Lidia Ghimpu
doctor, associate professor (docent), Institute of the Electronic Engineering and Nanotechnologies
Council's Members
- Anatolie Sidorenko, president
doctor habilitat, professor, Institute of the Electronic Engineering and Nanotechnologies - Elena Condrea, secretary
doctor, associate professor (docent) - Leonid Culiuc, member
doctor habilitat, professor, Institute of Applied Physics of the - Dormidont Şerban, member
doctor habilitat, Institute of Applied Physics of the - Vitalie Chistol, member
doctor, associate professor (docent), Technical University of Moldova
Theses
