The Effect of Thermal Annealing on the Properties of Indium Tin Oxide Thin Films

ITO thin films were deposited on glass substrates using e-beam evaporation. The influence of post-deposition annealing on the optical properties of the films was investigated in detail. It was found that the annealing conditions strongly affect the optical properties of the films. The transmittance of films annealed in forming gas (mixed 80% N ₂ and H₂) at first increases dramatically with increasing annealing temperatures up to 300degC but then drops for higher temperature anneals around 400degC. An interesting phenomenon is that the transmittance of the darkened film can recover under further 400degC annealing in air. Atomic force microscopy, X-ray diffraction and X-ray photoemission spectroscopy have been employed to obtain information on the chemical state and crystallization of the films. Analysis of this data suggests that incorporation and decomposition reactions of oxygen can be controlled to reversibly change the optical properties of the ITO thin film