ELECTRON SPECTROSCOPY STUDY OF Mo/Si(111) INTERFACES

Abstract

XPS and X-ray excited AES (XAES) have been used to follow the evolution of the electronic structure of the interface formed when submonolayer amounts of Mo atoms are evaporated onto clean Si(111) surface. The Mo 3d5/2 level undergoes a chemical shift of - 0.4 eV, towards lower binding energy, for surface coverage θ ≤ 1 monolayer (ML) and resumes its bulk value for θ ≤ 6 ML, while the Si 2p peak remains at the same position and the Si KLL feature increases weakly in kinetic energy. Si LVV Auger transitions indicate perturbations of the Si 3p states by the presence of Mo atoms. Annealings of thin deposits (~ 15 ML) at T > 500°C lead to the formation of stable and homogeneous MoSi2 layers. In comparison with the more investigated case of Ni/Si interfaces, the main differences are a weaker chemical shift of the Mo corelevels, an opposite charge transfer in the metal atoms and indication of a much more abrupt interface.