Preparation And Properties Of P-type Oxide Films And Transistors

In recent years, metal oxide thin film transistors?TFTs? received much attention in display and transparent electronic devices fields because of their superior electrical and optical properties. Most reports about oxide-based TFTs concentrated on n-type oxide TFTs, however, p-type oxide TFTs were rarely presented. This limited the application of TFTs in electronic display and complementary logic-based transparent electronics. Until now, the reports on p-type oxide TFTs were mainly focused on Cu₂O and SnO. The preparation method was mainly based on complex vacuum-based deposition techniques and the p-type oxide TFTs generally exhibited inferior electrical performance. In this paper, we fabricated p-type NiO and Cu₂O thin films by using the solution process and demonstrated the effect of the various annealing temperature on crystallinity, surface morphology and electrical property.NiO thin films were prepared by using sol-gel method and annealed in air. It was found that, the films deposited at different temperatures were amorphous and the surface roughness was enhanced with the increase of annealing temperature. The NiO thin film annealed at 500 o C exhibited the best electrical conductivity. Cu₂O thin films were fabricated by sol-gel method and annealed at different temperatures in vacuum atmosphere. The results showed that, the vacuum annealing process reduced CuO to Cu₂O and increased the crystallinity of the Cu₂O. The Cu₂O thin film annealed at 600 oC exhibited the best electrical conductivity. Then the Cu₂O-TFT was fabricated on SiO₂/Si substrate. According to the measurement, the Cu₂O-TFT annealed at 600 oC indicated the highest electrical performance with an on/off current ratio of 1.6 × 104,field-effect mobility of 0.29 cm2/V·s, threshold voltage of-3.2 V and subthreshold swing of 0.8 V/dec.