Influences of film thickness on the structural, electrical and optical properties of CuAlO2 thin films

• Film thickness plays an important role in the preferred orientation of CuAlO2 films.
• The electrical conductivity increases with increasing film thickness.
• The band gap decreases with increasing film thickness.
• The biggest of the figure of merit is achieved for the sample with the thickness around 165 nm.

CuAlO2 films with different thickness were prepared by the radio frequency magnetron sputtering technique. The structural, electrical and optical properties of CuAlO2 were studied by X-ray diffraction, atomic force microscope, UV–Vis double-beam spectrophotometer and Hall measurements. The results indicate that the single phase hexagonal CuAlO2 is formed and the average grain size of CuAlO2 films increases with increasing film thickness. The results also exhibit that the lowering of bandgap and the increase of electrical conductivity of CuAlO2 films with the increase of their thickness, which are attributed to the improvement of the grain size and the anisotropic electrical property. According to the electrical and optical properties, the biggest figure of merit is achieved for the CuAlO2 film with the appropriate thickness of 165 nm.