Thickness-dependent optoelectronic properties of CuCr0.93Mg0.07O2 thin films deposited by reactive magnetron sputtering

CuCr0.93Mg0.07O2 thin films were successfully deposited by DC reactive magnetron sputtering at 1123 K from metallic targets. The influence of film thickness on the structural and optoelectronic properties of the films was investigated. X-ray diffraction (XRD) results revealed that all the films had a delafossite structure with no other phases. The optical and electrical properties were investigated by UV-VIS spectrophotometer and Hall measurement, respectively. It was found that the optoelectronic properties exhibited a thickness-dependent behavior. The optical band gap and the average transmittance of the films showed a monotonous decrease with respect to the increase in thickness. The average transmittance in the visible region decreased from 67% to 47% as the thickness increased from ~70 nm to ~280 nm. Simultaneously, the conductivity of the films fell from 1.40 S∙cm−1 to 0.27 S∙cm−1. According to Haacke's figure of merit (FOM), a film with a maximum FOM value of about 1.72×10−7 Ω−1 can be achieved when the thickness is about 70 nm (σ≈ 1.40 S·cm−1 and Tav. ≈67%).