Micro-Structure Changes Caused by Thermal Evolution in Chalcogenide GexAsySe1−x−y Thin Films by In Situ Measurements

To understand the effects of thermal annealing on the structure of Ge_xAs_ySe_1-x-y thin films, the thermal evolution of these films was measured by the in situ X-ray diffraction (XRD) at different temperature (773 K or 1073 K) in a vacuum (10^-1 Pa) environment. The entire process of crystallization can be observed by using in situ XRD, which is from the appearance of a crystal structure to melting liquid-state and ultimately to the disappearance of the amorphous structure. In the crystallized process, the corresponding state-transition temperatures T_x (the onset crystallization temperature), T_l (the transition temperature from glassy-state to liquid-state), T_p (peak crystallization temperature) are linear with MCN (Mean Coordination Number). In order to obtain information about changes in the amorphous structural origin of the anneal-induced material, the samples were analyzed by in situ Raman spectroscopy. Analysis of the results through decomposing the Raman spectra into different structural units showed that the Ge-Ge, As-As, or Se-Se homopolar bonds as the nonequilibrium minority carriers could be found in films. It suggests that the formation of these bonds cannot be completely suppressed in any case, as one falls and another rises.