Comparative study of the structural, optical, and electrical properties of CuAlO2 thin films on Al2O3 and YSZ substrates via chemical solution deposition

Single-phase delafossite CuAlO2 thin films are deposited successfully on Al2O3 (001) and YSZ (100) substrates using the chemical solution method. X-ray diffraction data present that the CuAlO2 film on the Al2O3 (001) substrate is epitaxial, whereas that on YSZ (100) is c-axis oriented; the same is also demonstrated by the HRTEM images and SAED patterns. Optical transmittance spectra exhibit that both films have high transparency in the visible region. However, in this region, the optical transmittance of the CuAlO2 thin film deposited on (001) Al2O3 is inferior to that deposited on (100) YSZ. This optical anomaly can be attributed to surface scattering. Electrical transport measurements show that the resistivity of the film on (001) Al2O3 is one order lower than that on (100) YSZ, suggesting that in-plane orientation is significant in improving hole mobility.