Optical and Wetting Properties of CuAlO2 Films Prepared by Radio Frequency Magnetron Sputtering

The CuAlO2 films were prepared on glass and quartz substrates by radio frequency magnetron sputtering with a sintered target composed of Al(OH)3 and Cu2O powders. X-ray diffraction analyses reveal that the as-deposited films are amorphous structure and the as-annealed films are predominated by the CuAlO2 phase along with the Al2O3 phase. Scanning electron microscope (SEM) measurements indicate that grains grow up and surface becomes rougher as a result of increasing temperature. The optical studies show that annealing leads to the reduction of the average transmittance of the films from 60% to 40% for the visible range and the decrease of the fitted refractive index from 2.0 to 1.5. Direct band gaps confirmed by the transmittance and reflectance measurements are estimated to be 3.86 and 3.50 similar to eV for as-deposited and as-annealed films, respectively. As increasing exposure time, water contact angles of the as-deposited films exposed under ultraviolet light source 365 similar to nm or 254 similar to nm decrease from 96.3 degrees and 96.4 degrees to 87.5 degrees and 87.2 degrees, respectively. The variation of contact angle can be attributed to the hydrophobic organic stains on the surface, surface roughness, the formation of Cu2+, and band gap variation of CuAlO2 film. The as-annealed film becomes hydrophilic and its water contact angle is 31.1 degrees. The wetting property of CuAlO2 films is very important for the wide spread application of this material.