Stretched-exponential photoconductivity decay in nanocrystalline indium oxide

The effect of ultraviolet light irradiation on the conducting properties of the nanocrystalline In2O3 is studied. Nanocrystalline indium oxide thin films with various nanocrystals size are prepared by sol gel method. The mean nanocrystals size varies from 7-8 nm to 18-20 nm depending on conditions of their preparation. A large increase in conductivity by two to four orders of magnitude (depending on the nanocrystals size) is observed with light irradiation. The highly conductive state persists for a timescale of hours at room temperature after illumination. The relaxation rate of this persistent conducting state depends strongly on temperature and environment. The time-dependence of photoconductivity decay in our nanocrystalline In2O3 is governed by the stretched-exponential (William-Watts) relation. The stretched-exponential photo decay can be attributed to the motion of oxygen which exhibits dispersive diffusion with a characteristic power-law time dependence. (authors)