  The electronic structure of the transparent semiconductor In2O3 has been
studied by angle resolved photoemission spectroscopy upon deposition of
metallic indium and also tin on the surface of the semiconductor. By deposition
of metallic indium on In2O3 (111) single crystals, we detected the formation of
a free-electron like band of effective mass (0.38+-0.05) m0. At low coverages,
metallic In shifts the Fermi level of In2O3 to higher energies and a new
electronic state forms at the metal/semiconductor interface. This state of
two-dimensional character (2D-electron gas) is completely responsible for the
electrical conduction in In2O3 (111) at the surface region and has a band
dispersion, which does not correspond to the previously found surface
accumulation layers in this material. Despite the similarity of the electronic
properties of In and Sn, a larger downward banding was observed by Sn coverage,
which was not accompanied by the appearance of the surface state.
