Comparative study of the electronic structures of the In andSn/In2O3(111) interfaces

The electronic structure of the transparent semiconductor ${\mathrm{In}}₂{\mathrm{O}}₃$ 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 ${\mathrm{In}}₂{\mathrm{O}}₃$(111) single crystals, we detected the formation of a free-electron-like band of effective mass $(0.38\ifmmode\pm\else\textpm\fi{}0.05){m}₀$. At low coverages, metallic In shifts the Fermi level of ${\mathrm{In}}₂{\mathrm{O}}₃$ to higher energies and a new electronic state forms at the metal/semiconductor interface. This state of a two-dimensional character (2D electron gas) is completely responsible for the electrical conduction in ${\mathrm{In}}₂{\mathrm{O}}₃$(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 similarities of the electronic properties of In and Sn, a larger downward band bending was observed by Sn coverage, which was not accompanied by the appearance of the surface state.