We investigated p-type TeOx thin films fabricated by vacuum deposition using a mixture of TeO2 powder and W powder in Al2O3 crucibles and evaluated its thin-film transistor (TFT) characteristics. P-type TeOx thin films were obtained when W was added at a weight ratio of 15% or more relative to TeO2. However, the films became insulators and exhibited no electrical conductivity when the ratio was 10% or less. X-ray photoelectron spectroscopy analysis revealed that the TeOx thin films contained approximately 5% or more Te–Te bonds. Because W–O bonds exhibit a higher dissociation energy than Te–O bonds, TeO2 was considered to be reduced by W. In addition, W was not present in the film and was used solely for the reduction of TeO2. The results manifest that when TeOx TFTs are fabricated by vacuum deposition, the addition of an appropriate amount of reducing agent to the raw material is essential to form an adequate amount of Te–Te bonds.
Kato et al. (Mon,) studied this question.