Raman scattering of Ge-As-Se thin films

Abstract

Raman and infrared spectroscopy are efficient methods for obtaining information on the local structure of the disordered material, especially when the composition is varied. In particular, Micro-Raman spectroscopy have been used for study of the ternary glass system GexAsxSe1-2x, for which different composition in dependence of it mean coordination number Z exists in different phases - floppy, intermediate and stressed rigid. In this paper we report experimental results and analysis of Micro-Raman spectra for both thermally as-deposited and laser irradiated amorphous GexAsxSe1-2x (x=0.07; 0.09 and 0.14, Z=2.21; 2.27 and 2.42, respectively) thin films, of which glassy system situated in the region of floppy and intermediate phases. It was shown that for all investigated samples the measured Micro- Raman spectra consists from three vibrational modes located around ν=193 cm-1, ν=255 cm-1 and ν=475 cm-1. It was shown that position and intensity of these vibrational bands slightly depend on the composition and method of preparation. It was established that for Ge0.14As0.14Se0.72 composition with the mean coordination number Z=2.42, situated in the region of intermediate phase, the probability of existence of the tetragonal (pyramids As(Se1/2)3 and tetrahedral structural units Ge(Se1/2)4 is the same. For all samples of the glass composition Ge0.14As0.14Se0.72 the ratio of the intensity of both main vibration peaks centered around ν=193 cm-1 and ν=255 cm-1 remain unchanged.