Specific features of the optical and photoelectric properties of nanocrystalline indium oxide

The spectral dependences of the absorption coefficient and steady-state photoconductivity and the relaxation of photoconductivity (after illumination switch off) in nanocrystalline indium oxide (In$_2$O$_3$) films synthesized by the sol–gel method are investigated. The mean nanocrystal size varies from 7–8 to 39–41 nm, depending on the sample-preparation conditions. The optical band gap of nanocrystalline In$_2$O$_3$ is determined as a result of combined analysis of the optical absorption spectra and the spectral dependence of the photoconductivity. The optical band gap in nanocrystalline In$_2$O$_3$ is found to be much narrower than the optical band gap in In$_2$O$_3$ single crystals. The photoconductivity decay kinetics in nanocrystalline In$_2$O$_3$ in air, vacuum, and argon at room temperature are studied. A model explaining the observed photoconductivity decay is proposed.