XAFS Study of CdTe1-xSx Semiconductor Glass Composites

We have measured the X-ray absorption spectra of CdTel.,SX nanocrystals grown in a borosilicate matrix, for X = 0, 0.1, 0.4 and 0.7. The appearance and the growth of the nanocrystals in isothermal heat-treatment at 580°C, observed in optical measurements, were correlated to the evolution of the XANES at the cadmium edge corresponding to the progressive substitution of oxygen atoms by chalcogens atoms. The final mean environment of the cadmium atoms in nanocrystals seems to be closer to CdS than to CdTe, for any value of X. On the other hand significant deviations from CdO pure environment were observed in non-treated samples, correlated to the increase in the sulfur content in the initial glass. These features were ascribed to the existence of early CdS clusters.