In-Situ Raman Spectroscopy Study of Photoinduced Structural Changes in Ge-rich Chalcogenide Films

Very few studies have been directed at the compositional dependence of the intrinsic photostability of the GexSe1-x binary ChG films especially for the Ge-rich films with the mean coordination number (MCN) larger than 2.67. Here, by measuring the in-situ transmission changes, it shows that the photosensitivity (e.g., photobleaching, PB) of the Ge-rich films (as compared to the GeSe2 film) is attenuated, in fact almost completely eliminated in the film with the largest MCN. A straightforward technique, in-situ Raman spectroscopy, is used to record the time-resolved intrinsic structural changes during the irradiation of the films. The result indicates a transition from PB towards photostability occurs at the critical composition of GeSe2 corresponding to the structural phase transition. The stressed rigid structures of the Ge-rich films inhibit any significant photo-structural changes.