CHEMICAL INTERACTIONS AND SCHOTTKY-BARRIER DETERMINATIONS AT THE MG/SI(100) INTERFACE STUDIED USING X-RAY PHOTOELECTRON-SPECTROSCOPY

Low work function metal-on-semiconductor systems have technological importance as efficient photocathodes or as thermionic energy converters. Mg-on-Si provides one such system that we have studied here. When the metal is deposited onto Si(100) at room temperature, it reacts to form a thin (approximately two monolayers) layer of Mg2Si. Upon further deposition, the silicide behaves as a reaction barrier preventing the reactants coming into contact. Mg metal therefore grows on top of the silicide. Furthermore, it adopts a layer-by-layer growth mode. The Schottky barrier formed at this interface is very close in value to that quoted by Monch [Phys. Rev. Lett. 58 (1987) 1260], i.e. approximately 0.5 eV. This close agreement suggests that the final pinning position may be a consequence of metal-induced virtual gap states.