Thin film growth and band lineup of In2O3 on the layered semiconductor InSe

Abstract

Thin films of the transparent conducting oxide ${\mathrm{In}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ have been prepared in ultrahigh vacuum by reactive evaporation of indium. X-ray diffraction, optical, and electrical measurements were used to characterize properties of films deposited on transparent insulating mica substrates under variation of the oxygen pressure. Photoelectron spectroscopy was used to investigate in situ the interface formation between ${\mathrm{In}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ and the layered semiconductor InSe. For thick ${\mathrm{In}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ films a work function of $\text{φ=4.3\hspace{0.05em}}\mathrm{eV}$ and a surface Fermi level position of $E_F{\mathrm{-E}}_V\text{=3.0\hspace{0.05em}}\mathrm{eV}$ is determined, giving an ionization potential $I_P\text{=7.3\hspace{0.05em}}\mathrm{eV}$ and an electron affinity $\text{χ=3.7\hspace{0.05em}}\mathrm{eV}.$ The interface exhibits a type I band alignment with ${\mathrm{\Delta E}}_V\text{=2.05\hspace{0.05em}}\mathrm{eV},$ ${\mathrm{\Delta E}}_C\text{=0.29\hspace{0.05em}}\mathrm{eV},$ and an interface dipole of $\text{δ=−0.55\hspace{0.05em}}\mathrm{eV}.$