Study On The Preparation And Optical Electrical Properties Of Transparent Conductive CuAlO₂ Thin Films

The delafossite structure, p-type and directly band-gap electrical conductivity transparent oxide thin film of CuAlO2 was designed by Kawazoe in 1997 for the first time. Using CAO films, ozonoscope and transparent photoelectricity sheet were manufactured successfully. CuAlO2 has become the hot spot of the area of transparent and conductivity film.In this paper, high quality CAO thin films were prepared by direct current (DC) reactive magnetron sputtering method using CAO target (99.99%)。XRD, SEM, XPS, UV-Vis and IR spectroscopy were used to characterize the films. The conduction mechanism was analyzed and the electrical properties were investigated by Van der Pauw method. The influence of the annealing temperature and Oxygen argon (O2/Ar) ratio for the optical and electrical properties were studied.SEM results show that the surfaces morphology of the films was smooth and the surface roughness was small. The films were composed of some excellent columnar crystallites. The XPS results indicated that the Cu exist as +1 valence charge and Al exist as +3 valence charge,this is the same in the CAO.The spectral analysis result indicate that the transmission rate of the thin film 80%, The transmission rate was decrease if the substrate temperature and oxygen argon ratio raise increases. The transmission rate will increaseif rise the work pressure and distance of target. Along with the annealing temperature increase, the transmission rate of the thin film also increases, and the absorbance edge move toward the short wavelength. along with the sputtering time increase, the transmission rate will decrease, the transmission rate of the thin film increase too.The results of the electrical properties indicate that annealing temperature and oxygen argon ratio have strong influence the properties of CAO films. The resistivity of the CAO films decreases as the annealing temperature increasing, but the carrier concentration and mobility increases. The resistivity increases while the mobility increases as decreasing the oxygen argon ratio.Based on the studied of the structural, optical and electrical properties of CAO thin films, it can be obtained the optimal deposition conditions of CAO thin films by direct current reactive magnetron sputtering. The oxygen argon ratio, deposition temperature, gas pressure, distance of target and substrate, sputtering power and annealing temperature were 16/24,200℃,5Pa,7.0cm, 57W,1200℃, respectively. At these conditions, the transmittance and resistivity of CAO thin films prepared by DC magnetron sputtering method is 80% and 5.9?.cm, respectively.