Stoichiometric and Structural Origin of Electronic States at thePd2Si-Si Interface

Extra Si density of states has been observed within about 3-4 Å of the ${\mathrm{Pd}}_2$Si-Si(111) interface. Spectral analysis indicated that most of these states exist near the Si band-gap region and originate from an atomic environment more Si rich than ${\mathrm{Pd}}_2$Si. Transmission-electron-microscopy lattice images showed a structurally sharp ${\mathrm{Pd}}_2$Si-Si interface with misfit dislocations and atomic-step imperfections. It is suggested that the interfacial bonding in such a structure can account for the observed interface states.