Influence of annealing temperature and environment on the properties of indium tin oxide thin films

Abstract

Indium tin oxide (ITO) thin films were deposited on glass substrates using the e-beam evaporating technique. The influence of deposition rate and post-deposition annealing on the optical properties of the films was investigated in detail. It is found that the deposition rate and annealing conditions strongly affect the optical properties of the films. The transmittance of films greatly increases with increasing annealing temperature below 300°C but drastically drops at 400°C when they are annealed in forming gas (mixed N2 and H2 gas). An interesting phenomenon observed is that the transmittance of the darkened film can recover under further 400°C annealing in air. Atomic force microscopy, x-ray diffraction and x-ray photoemission spectroscopy were employed to obtain information on the chemical state and crystallization of the films. Analysis of these data suggests that the loss and re-incorporating of oxygen are responsible for the reversible behaviour of the ITO thin films. © 2005 IOP Publishing Ltd.