Preparation Technology Optimazation And Porperties Of P-type Transparent Conductive Oxide CuCrO₂ Thin Films

Delafossite-CuCrO2 is a p-type oxide semiconductor. It has high visible light transmittance and conductivity, and the band gap is 3.2eV. The CuCrO2 thin films can be applied to photoelectronics, such as:transparent electrode, solar cells, flat panel display, special window coating and so on. The holes in CuCrO2 mainly originate from the interstitial oxygen, Cu vacancies and Cr vacancies. The conductivity of CuCrO2 is much smaller than the conductivity of n-type semiconductor, because of the relatively low mobility of the holes. Therefore, how to improve the conductivity of CuCrO2 has become a research hotspot. In this dissertation, CuCrO2 film was prepared by RF magnetron sputtering method on the quartz glass substrate. The effects of the ratio of O2 to Ar, working pressure and annealing temperature on the structure and optical properties of CuCrO2 films were investigated by XRD, scanning electron microscope and ultraviolet-visible spectrophotometer. The p-CuCrO2/n-Si heterojunction was prepared after optimizing the film preparation process, and its I-V characteristics were investigated. The main results were as follow:1).The CuCrO2 films prepared with different the ratio of O2 to Ar are 3R delafossite structure. With the increase of the ratio of O2 to Ar, the (006) diffraction peak of CuCrO2 films exists, and the (110) peak gradually disappears, the CuO phase and the CuCr2O4 phase also disappear. Oxygen as reactive gas will affect the growth orientation of the film. With the increase of the ratio of O2 to Ar, the light transmission properties of CuCrO2 thin films decrease, and the optical band gap of the films become small. The absorption edge of the films move toward the long wavelength. When the ratio of O2 to Ar is zero, the transmittance of the film is biggest, which is 79%, and the optical band gap is about 3.06eV.2).The CuCrO2 films prepared with different working pressure are 3R delafossite structure. With the increase of the working pressure, the films become smoother, and the thickness of the films become small gradually. When the working pressure is 1.0Pa, the FWMH of the films are smallest, it shows that the crystallization of the films are best. With the increase of the working pressure, the transmittance of the film increases. Whenthe working pressure is 4.0Pa, the average transmittance of the film is biggest, which is 80%. With the increase of the working pressure, the optical band gap of the films become small, and the absorption edge of the films move toward the long wavelength.3).CuCrO2 films were prepared with different annealing temperature. The as-deposited CuCrO2 film is amorphous. The films transform to crystallization after annealing, and the films have 3R delafossite structure. With the increase of the annealing temperature, the CuO phase decreases gradually, and the crystallization degree of CuCrO2 films increases. When the annealing temperature is over 800℃, the CuO phase increases, it shows that when the annealing temperature is too high, CuCrO2 may resolve. With the increase of the annealing temperature, the visible light transmittance of the film and the optical band gap of the films increase gradually. The absorption edge of the films move toward the short wavelength. When the annealing temperature is 800℃, the film has the best transmittance, which is 70%, and the optical band gap is about 3.06eV.4).The CuCrO2 film prepared on the Si substrate becoming p-CuCrO2/n-Si heterojunction. The films prepared with different annealing temperature have 3R delafossite structure, and there are no other impurity phases in the films. With the increase of the annealing temperature, the particles of the film become small and more uniform, the density of pore defects in the films decreases, the crystallization degree of the films increases, the film becomes smooth and compact.5).The p-CuCrO2/n-Si heterojunctions prepared with different annealing temperature have obvious rectifying characteristics. With the increase of the annealing temperature, the rectifying characteristics of the heterojunction become better. The turn-on voltage of the heterojunction decreases. When the annealing temperature is 850℃, the turn-on voltage of the heterojunction is smallest, which is 0.2V. In the bias voltage of ±2.0V, the absolute value of the ratio of forward current and reverse current is about 73.