| Autor: |
E. Mitylineou, P. Petkov, M. Skaperda, Y. Nedeva, T. Petkova |
| Rok vydání: |
2002 |
| Předmět: |
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| Zdroj: |
Proceedings of the Second International Symposium of Trans Black Sea Region on Applied Electromagnetism (Cat. No.00TH8519). |
| DOI: |
10.1109/aem.2000.943238 |
| Popis: |
Summary form only given. A study of the optical spectra of amorphous GeSe/sub 4/Ga/sub x/ and GeSe/sub 5/Ga/sub x/ chalcogenides in the spectral range 460 nm-1400 nm is performed.. Samples used were in a bulk and thin film form. Bulk glasses are prepared by monotemperature synthesis from elements with 4N purity in evacuated quartz ampoules. Thin films were deposited by vacuum evaporation at a residual pressure of 10/sup -3/ Torr using optical glass as the film substrate. For the measurements the samples were placed in the cryostat and kept in vacuum. A 75 W halogen lamp with monochromatic light was used to illuminate the sample. The intensity of exident and transmitted light through the sample was measured with a silicon detector at the lower and a germanium detector at the longer wavelength. From the absorption spectra the optical energy gap (E/sub g//sup 4/) was determined. The optical-absorption edge is described using the non-direct transition model proposed by Tauc and the optical band gap-E/sub g//sup T/ is calculated from the absorption coefficient values by Tauc's procedure. Optical absorption was described in the medium-absorption region, according to Urbach's rule and the slope of the Urbach tail was calculated. The compositional dependence of the band gap was discussed. A relation between the average coordination number, composition and optical characteristics was obtained. From the transmission spectra, the optical constants were calculated using an optical-characterisation method based on creating the upper and the lower envelope curves of the spectrum. The values of the refractive index and absorption coefficient are consider as a function of the average coordination number (z) of covalent bonds per atom. The observed regularities are related to some structural pecularities in the ternary systems investigated. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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