Photoreduction and oxidation behavior of In2O3 nanoparticles by metal organic chemical vapor deposition

Abstract

In 2 O 3 nanoparticles were synthesized at low substrate temperatures by the metal organic chemical vapor deposition technique. Nanoparticles with a mean diameter from 3 to 33 nm can be obtained by varying the growth temperature. Photoreduction and oxidation studies were carried out for particle-containing layers exhibiting a resistance change of more than five orders of magnitude after ultraviolet irradiation and oxidation by ozone. A grain boundary model was proposed to understand the photoreduction and oxidation mechanism for the nanoparticle layers. It was suggested that by photoreduction the nanoparticles are reactivated throughout the layer. The Schottky barrier between the nanoparticles decreases inducing a reduction of the space-charge-limited region. After oxidation, a completely depleted space-charge region covering the whole volume of In2O3 nanoparticles is formed. Furthermore, the bulk diffusion process dominates the response of thick layers during the oxidation process. By decreasing the layer thickness down to 10 nm, surface effects dominate, resulting in an ultrafast response to changes in ozone concentration. The typical response time of very thin In2O3 nanoparticle layers was determined to be less than 1 s.