Low energy electron loss spectroscopy of Si–Ge interfaces

We present energy loss spectra of Si–Ge heterojunctions. The early stage of formation of the interface has been studied by successive evaporations of small amounts of germanium on a silicon substrate heated at 350 °C. The results, compared with theoretical calculations, show that the interface is abrupt on a microscope scale and that germanium induces extrinsic interface states in the main and partial gaps of the projected bulk band structure of silicon on the (111) surface.