Effect of the tin impurity on the energy spectrum and photoelectric properties of nanostructured In$_2$O$_3$ films

It is shown that the doping of colloidal indium-oxide nanocrystals with tin shifts the absorption edge to shorter wavelengths of the visible spectral region and induces considerable absorption in the infrared region. The shape of the absorption and transmittance spectra in the infrared region is characteristic of the local surface plasmon resonance. According to estimations, the concentration of free charge carriers in In$_2$O$_3$(Sn) reaches 10$^{19}$ cm$^{-3}$. The temperature dependences of the photoconductivity in the range 77–300 K are indicative of hopping conduction in nanostructured films based on In$_2$O$_3$(Sn) nanocrystals. The mechanisms responsible for the effect are discussed.