Effects of Mg substitution on the structural, optical, and electrical properties of CuAlO2 thin films

Mg-doped CuAlO2 thin films are prepared by the chemical solution method. The XRD results show that the solid solubility of Mg species on Al sites in CuAlO2 lattice is lower than 2 at.%. When less than 2 at.% of Mg is added to the CuAlO2 film, the surface roughness of the films was reduced with Mg substitution. Moreover, the c-axis orientation of the films improves because the in-plane fusion between CuAlO2 crystallites is hindered. Optical and electrical measurements show that substituting Al3+ in the films with Mg2+ increases both their transmittance in the visible region and their optical band gaps. As well, their electrical conductivity is enhanced. At 300 K, the conductivity of the 1 at.% Mg-doped sample is up to 5.2 × 10−3 S/cm. Thus, Mg-doped CuAlO2 films may have potential applications as transparent conductive oxides.

Research highlights▶ Mg-doped CuAlO2 thin films were prepared by chemical solution deposition (CSD) process. As a simple preparation route, CSD has its unique advantages, such as homogeneity at the molecular level, easy introduction of dopants, high deposition rate, non-vacuum deposition. ▶ CuAl1−xMgxO2 thin films produced by CSD method have high optical transparency, comparable even to the film prepared by other physical methods despite their slightly lower electrical conductivity. ▶ Through comparing with the results reported by other researchers, some novel phenomena were observed in our experiments, such as the decreased solubility of Mg species, the enhancement of c-axis orientation, the decrease of surface roughness, the increase of optical band gaps and the variation of transmittance in the ultraviolet region.