Electronic Property of Thin Single-Crystal Films of α-Al₂O₃ on Ru(0001)

Abstract

High-quality single-crystal films of α-Al₂O₃ with various thicknesses below 35Å have been fabricated on the Ru(0001) surface. The phase transtion from γ- to α-Al₂O₃ has been used for fabrication. The thickness dependence of the band gap for the oxide layer has been measured by the interband transition using electron energy loss spectroscopy. The band gap has been found to decrease with decreasing oxide thickness. The same tendency of this extraordinary result has been observed in scanning tunneling spectroscopy. These results can be interpreted by the many-body effect.