INSB-CDTE INTERFACES - A COMBINED STUDY BY SOFT-X-RAY PHOTOEMISSION, LOW-ENERGY ELECTRON-DIFFRACTION, AND RAMAN-SPECTROSCOPY
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abstract
CdTe layers have been deposited on c(28) (100) InSb and cleaved (110) InSb substrates under molecular-beam epitaxy conditions at room and elevated temperatures. The low-energy electron diffraction and soft x-ray photoemission spectroscopy (XPS) results show that the interfaces formed at room temperature are reasonably abrupt, though disordered. Deposition on substrates at elevated temperatures, however, leads to a nonabrupt interface and new chemical phases. The thickness of the intermediate layer formed increases with substrate temperature and is shown to be semiconducting by the soft XPS measurements. It is suggested that the layer predominantly consists of In2Te3. In order to investigate this further, Raman spectroscopy studies have been carried for CdTe layers on InSb prepared at both room and elevated temperatures and also on In2Te3 crystals. The spectra obtained clearly indicate the existence of excess Te at the room temperature interface, whereas In2Te3 and segregated Sb were observed at elevated temperature interfaces. The thickness of the intermediate layer has been estimated using the half-widths of the Raman signal. The results have been compared with thermodynamical considerations and points of interest are discussed.
