Electronic structure of In₂ O₃ and Sn-doped In ₂ O₃ by hard x-ray photoemission spectroscopy

The valence and core levels of In2 O3 and Sn-doped In2 O3 have been studied by hard x-ray photoemission spectroscopy (hν=6000 eV) and by conventional AlKα (hν=1486.6 eV) x-ray photoemission spectroscopy. The experimental spectra are compared with density-functional theory calculations. It is shown that structure deriving from electronic levels with significant In or Sn 5s character is selectively enhanced under 6000 eV excitation. This allows us to infer that conduction band states in Sn-doped samples and states at the bottom of the valence band both contain a pronounced In 5s contribution. The In 3d core line measured at hν=1486.6 eV for both undoped and Sn-doped In₂ O₃ display an asymmetric lineshape, and may be fitted with two components associated with screened and unscreened final states. The In 3d core line spectra excited at hν=6000 eV for the Sn-doped samples display pronounced shoulders and demand a fit with two components. The In 3d core line spectrum for the undoped sample can also be fitted with two components, although the relative intensity of the component associated with the screened final state is low, compared to excitation at 1486.6 eV. These results are consistent with a high concentration of carriers confined close to the surface of nominally undoped In₂ O₃. This conclusion is in accord with the fact that a conduction band feature observed for undoped In₂ O ₃ in AlKα x-ray photoemission is much weaker than expected in hard x-ray photoemission.