Electronic surface properties of a liquid semiconductor: selenium

Abstract

The electronic properties of liquid, amorphous and trigonal Se have been studied by photoemission and reflectance spectroscopy near the energy gap. Sharp valence band edges with no observable tailing were found for the amorphous and liquid phases. On liquid Se a surface photovoltage of 0.4 eV was observed upon secondary illumination. This corresponds to a pinning of the surface Fermi level by mid-gap states and provides the first evidence for 'surface states' on a liquid semiconductor. It is proposed to relate them to an accumulation of intrinsic structural defects at the surface.