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Phonon and Stability Properties in Two Novel Chalcogenide Solids Investigated by Raman Scattering Using High-Pressure and Photocrystallization Experiments
Başlık:
Phonon and Stability Properties in Two Novel Chalcogenide Solids Investigated by Raman Scattering Using High-Pressure and Photocrystallization Experiments
Yazar:
Gross, Nelson, author.
ISBN:
9780438047327
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (101 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: Bernard A. Weinstein Committee members: Athos Petrou; Hao Zeng.
Özet:
The research presented in this doctoral thesis examines two novel chalcogenide (containing group XVI elements) materials, crystalline BaZrS3 and glassy-phase GexSe1-x alloys. The optical phonons in these materials are investigated by means of Raman spectroscopy, and changes in their phonon spectra are explored using high-pressure and photo-crystallization experiments, respectively, for the BaZrS3 and GexSe 1-x studies. As an important parallel result, useful insight is gained into the phase stability of these two materials. A brief background theory of Raman scattering is laid out since it is the primary tool of investigation for the two main areas of study. The first study presented is for BaZrS 3, a chalcogenide-based distorted perovskite solid. The research on this material chiefly concerns the investigation of its 24 Raman active phonons, which are measured and successfully identified by comparison to theory, and then studied in experiments as a function of pressure at two different temperatures. The pressure-Raman studies presented show that BaZrS3 maintains its distorted perovskite structure up to 8.9 GPa, indicating its structural stability and making it a suitable candidate for band gap tuning via alloying for photovoltaic applications. The second area of research examines photo-induced crystallization inside low Ge concentration (1%--9% Ge) amorphous Ge xSe1-x films. As a pre-requirement for this study, a non-destructive method of determining the average Ge concentration inside these films was developed utilizing Raman spectroscopy. The method was accurate to within +/- 0.5% within the low Ge content regime of interest. These films were then tested for photo-induced crystallization and results show that films containing more than 4.6--6.5% Ge are stabilized against crystallization of amorphous Se into crystalline trigonal Se within the film. This result is compared to similar findings for amorphous AsxSe 1-x films and a likely explanation of the similarities is proposed in terms of nucleation theory. The minimum crystallite volume needed to nucleate trigonal Se in these glasses is estimated to be ~ 560--400 A 3.
Notlar:
School code: 0656
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(679929.1) | 679929-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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