Huge charge transfer from potassium on H:Si(111)-(1×1)

Abstract

Potassium adsorption on the hydrogen-terminated H:Si(111)-(1×1) surface is studied by high-resolution core-level and valence-band photoelectron spectroscopy. New light is shed on the interpretation of core-level spectra at the K/Si(111) interface. Low potassium coverages induce a large downward band bending. The Fermi level moves ∼0.26 eV above the conduction band minimum, which is explained by a huge charge transfer from the adsorbate to the semiconductor bulk. For room-temperature saturation coverage, the Fermi level drops back into the semiconductor band gap. This leads to a vanishing n-type Schottky barrier height Φ (n)=0.02±0.03 eV in agreement with theoretical results.