Fabrication Of P-type NiO Transparent Conducting Thin Films And Research Of Its Diode Based On Si

NiO is a promising wide-bandgap oxide semiconductor with direct band gap between 3.6 eV and 4.0 eV at room temperature. NiO has many unique properties because of its electrical structure and p-type conductivity, which leads to its wide application in transparent displays, gas sensors, ultraviolet detection etc. Study on n-type transparent oxide semiconductors has been well conducted, but research on p-type transparent oxide semiconductors is in a slower pace. Therefore, it is critical to find out practical methods to fabricate NiO thin films.In this thesis, thermal oxidation with ultraviolet(UV) light is proposed to fabricate NiO thin films. By observing the effects of oxidation time, UV light, annealing condition and doping on NiO thin films, experiment conditions are optimized. N-NiO/p-Si heterojuction device is successfully made. The main content of the thesis includes:1. fabrication of NiO thin films and optimization of experiment conditionsFabrication of NiO thin films are divided into two parts, deposition of Ni thin film and oxidation of Ni film. Crystal structure and optical characteristic of NiO thin films vary as experiment conditions change. NiO samples made by 60 minutes’ oxidation have the highest peak in Raman spectroscopy, indicating the lowest resistivity of the thin film. Metal-halide lamp and Hg-ozone lamp with power density of 600 mW/cm2 are used to catalyze the oxidation. Annealing in nitrogen for 30 minutes contributes to decreasing crystal damage, thus improving the performance of the film. NiO films doped by lithium have worse transparency. According to XRD graphs, the crystal structure of NiO remains the same, but its growing preference changes.2. fabrication of p-NiO/n-Si heterojunction device and its electrical characterizationIn order to measure the current and voltage of the heterojunction, metal electrodes are deposited on the surface of NiO and Si and p-NiO/n-Si heterojunction device is successfully made. Platinum is selected as contact to NiO due to its high work function. The I-V characteristic is almost linear thus the contact can be approximated to ideal ohmic contact. NiO/Si heterojunction device without doping shows good rectification. Li doping helps decrease leakage current under reverse bias. Visible lights have no effect on the diode under positive bias, but they can increase leakage current depending on their wavelengths. C-V characteristic of the diode is measured under different frequencies. Good linearity is observed between 1/C~2 and V.