Geometric and electronic structures of monolayer potassium fullerides on Si(111)-√3×√3-Ag

Abstract

Metal-terminated silicon surfaces are a specific class of templates for growth of fulleride ultrathin films. Using scanning tunneling microscope and spectroscope, we investigate the geometric and electronic structures of KxC60 monolayers on Si(111)-√3×√3-Ag with x gradually increased to 2. Besides long-range ordered KC60 and K2C60 monolayers, a fraction-stoichiometric fulleride, K4/3C60 monolayer, is newly discovered. All these fulleride monolayers open an energy gap at the Fermi level owing to electronic correlations and Jahn-Teller distortion. The gap of the even-stoichiometric fulleride, K2C60, is prominently softened by partial electron doping from the Si(111)-√3×√3-Ag surface.