Characterization of delafossite-CuCrO2 thin films prepared by post-annealing using an atmospheric pressure plasma torch

Abstract

This study reports the preparation of delafossite-CuCrO2 thin films were prepared on quartz substrates using sol–gel processing and post-annealing with an atmospheric pressure plasma torch. The films were first deposited on a quartz substrate by spin coating. The specimens were then annealed at 500°C in air and post-annealed with an atmospheric pressure plasma torch with N2–5% O2 at 650°C for 20min. The specimens annealed in air exhibited CuO and CuCr2O4 phases. Post-annealing using an atmospheric pressure plasma torch obtained the pure CuCrO2 (delafossite, R3¯m) phase. The binding energies of the Cu-2p3/2 and Cr-2p3/2 peaks of the CuCrO2 thin films were centered at 932.1±0.2eV and 576.1±0.2eV, which revealed the valence state of Cu+ and Cr3+ in the films. The chemical composition of CuCrO2 thin films was close to the stoichiometry. As the CuCrO2 phase formed, the film surface began to exhibit agglomerate features and the cross-sectional morphology showed an equiaxed grain feature. The average transmittance of CuCrO2 thin films was approximately 66% in the visible region. The direct optical bandgap of CuCrO2 thin films was 3.08eV, which is consistent with reported data in the literature. The positive Seebeck coefficients of the CuCrO2 thin film prepared by post-annealing using an atmospheric pressure plasma torch confirmed the p-type characteristics of the film. The electrical conductivity of CuCrO2 thin films was 2.7×10−2Scm−1 with a carrier concentration of 2.8×1013cm−3. Hence, post-annealing using an atmospheric pressure plasma torch is an effective tool and a feasible method for preparing transparent conductive delafossite thin films.