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Optical spectroscopy of chalcogenide glasses (As4S3Se3)1-xSnx


Author: Iaseniuc Oxana
Degree:doctor of physics and mathematics
Speciality: 01.04.10 - Semiconductors physics and engineering
Year:2015
Scientific adviser: Mihail Iovu
doctor habilitat, professor, Institute of Applied Physics of the ASM
Institution: Institute of Applied Physics of the ASM

Status

The thesis was presented on the 20 November, 2015
Approved by NCAA on the 22 December, 2015

Abstract

Adobe PDF document1.71 Mb / in romanian
Adobe PDF document1.36 Mb / in russian

Thesis

CZU 621.315.592.539.213

Adobe PDF document 9.57 Mb / in russian
0 pages


Keywords

chalcogenide glasses, amorphous films, optical absorption, refractive index,X-ray diffraction, Raman spectroscopy, recording mediums

Summary

The thesis is written in Russian and includes the Introduction, 4 Chapters, Conclussions and Recommendations, Bibliography with 154 references, 113 pages, 95 figures, and 6 tables. The obtained results were published in 24 scientific works (of which 6 are articles).

The purpose of the thesis was the investigation of the fundamental properties of chalcogenide glasses and amorphous films (As4S3Se3)1-xSnx, the determination of their optical parameters and their modifications under the action of external factors, the study of the process of optical information recording.

In main outcome of the investigations was obtained the solution of a major scientific problem, which consists in the control of the physical and optical properties of chalcogenide glasses and amorphous films (As4S3Se3)1-xSnx by changing their composition and under the action of external factors.

The scientific novelty and originality of the obtained results
For the first time a study of the physical, mecanical, optical, photovoltaic, and holographic properties of (As4S3Se3)1-xSnx chalcogenide glasses and thin amorphous layers has been carried out. It was established that doping of chalcogenide glasses of (As4S3Se3)1-xSnx with tin impurities, especially doping of x=0,04 of tin, essentially reduces the intensity of some absorption bands of S-H and H2O. Increasing the tin concentration up to x=0,10 shifts the vibration modes into the Raman spectra situated at frequencies ν=236 сm-1 (pyramids AsSe3/2) and ν=345 сm-1 (pyramids AsS3/2) toward the low frequencies region.

It was also established that, when the Sn concentration in (As4S3Se3)1-xSnx chalcogenide glass increases, there is a shift of the fundamental absorption edge in the red region. The optical band gap Eg opt values from the optical absorption spectra were calulated, and its dependence on the amorphous films composition was established. From the optical transmittance spectra, the values of the absorption coefficient α, refractive index n, dispersion energy E0, and dielectric oscillator strength Ed were determined, as well as the degree of the optical parameters modulation under the light action with energy hν≥ Eg opt.

The process of the optical transmission relaxation T(t)/T(0)=f(t) for amorphous layers of (As4S3Se3)1-xSnx under light exposure of He-Ne laser was studied „in-situ”, and can be described by the stretched exponential function: T(t)/T(0)=A0+Aexp[-(t-t0)/τ](1-β). In (As4S3Se3)1-xSnx thin films, the diffractive gratings were recorded using the holographic method and the electron-beam irradiation. During the process of the diffraction gratings recording, the relief modulation on the films surfaces at high electron-beam currents was detected.

The obtained results show an interest for materials science of amorphous semiconductor materials. Amorphous films of the studied chalcogenide glasses of (As4S3Se3)1-xSnx can be used in holography as the optical information recording media and as well as for diffraction optics, as the diffractive structures written using the electron beam.