X-ray diffraction and Raman spectroscopy studies of Ga-Ge-Te alloys

The structure and vibrational properties of glassy Ge19Te81 and Ga7.9Ge11.5Te80.6 alloys were studied using X-ray diffraction and Raman spectroscopy. The amorphous nature of the obtained alloys was confirmed by the experimental X-ray diffraction patterns. The latter were used for calculating radial distribution functions. Such calculations gave the positions of the nearest-neighbour peak r1 – 2.65 Å and second nearest-neighbour peak r2 – 4.31 and 4.44 Å. The obtained r1 values are in good agreement with the known from literature Ge-Te and Ga-Te bond lengths. Similar r1 values were also observed for Ga-Ge-Te glasses of different compositions. The r2/r1 values of 1.63 and 1.68 are close to the typical value for a regular tetrahedron structure. The observed bands in the Raman spectra of the studied Ga-Ge-Te samples show that such glasses contain different nanophases. The Raman spectra may be interpreted in terms of vibrational modes of Ga-Te and Ge-Te binary glasses and films.