The Optoelectronic Properties of p-Type Cr-Deficient Cu[Cr_0.95-xMg_0.05]O₂ Films Deposited by Reactive Magnetron Sputtering

CuCrO₂ is one of the most promising p-type transparent conductive oxide (TCO) materials. Its electrical properties can be considerably improved by Mg doping. In this work, Cr-deficient CuCrO₂ thin films were deposited by reactive magnetron sputtering based on 5 at.% Mg doping. The influence of Cr deficiency on the film's optoelectronic properties was investigated. As the film's composition varied, CuO impurity phases appeared in the film. The mixed valency of Cu⁺/Cu²⁺ led to an enhancement of the hybridization between the Cu3d and O2p orbitals, which further reduced the localization of the holes by oxygen. As a result, the carrier concentration significantly improved. However, since the impurity phase of CuO introduced more grain boundaries in Cu[Cr_0.95-xMg_0.05]O₂, impeding the transport of the carrier and incident light in the film, the carrier mobility and the film's transmittance reduced accordingly. In this work, the optimal optoelectronic performance is realized where the film's composition is Cu[Cr_0.78Mg_0.05]O₂. Its Haacke's figure of merit is about 1.23 × 10^-7 Ω^-1.