A structural study of gallium lanthanum sulphide glass bulk and thin films by x-ray absorption fine structure spectroscopy

Atomic-scale structure changes in gallium lanthanum sulphide bulk glass and ablation-deposited thin films have been studied by the x-ray absorption fine-structure (EXAFS) technique. EXAFS spectra have been recorded at the sulphur and gallium K edges, and the lanthanum L-3 edge, and this has allowed us to construct a detailed picture of the local structure in bulk glass and thin films. The EXAFS results indicate that there is chemical disorder in the structural network of the GLS thin films, although chemical ordering is predominant in bulk GLS glass. The existence of 'wrong bonds', i.e. Ga-Ga and S-S bonds, in the structure has been discussed and correlated with optical absorption experiments undertaken on the same samples to provide a consistent picture of the local structure.