Characterization of transparent conductive delafossite-CuCr1-xO2 films

In this study, the CuCr1-xO2 films with x = 0.00-0.25 were prepared on a quartz substrate by sol-gel processing. The films were first deposited onto a quartz substrate by spin-coating. The specimens were annealed at 500 degrees C in air for 1 h and post-annealed in N-2 at 700 degrees C for 2 h. As the films were post-annealed in N2, a pure delafossite-CuCrO2 phase appeared in the CuCr1-xO2 films below x = 0.20. However, an additional CuO phase appeared at x = 0.25. The pure delafossite-CuCrO2 phase can exist within x = 0.20 in CuCr1-xO2 films. The binding energies of Cu-2p(3/2) and Cr-2p(3/2) in the CuCr1-xO2 films with the pure delafossite-CuCrO2 phase were 932.1 +/- 0.2 eV and 576.0 +/- 0.2 eV, respectively. The surface exhibited elongated grain features when the pure delafossite-CuCrO2 phase was present in the CuCr1-xO2 films. The maximum transmittance of the CuCr1-xO2 films with the pure delafossite-CuCrO2 phase was approximately 80%, which moved toward the visible region with the increasing x-value. The film absorption edges were observed at 400 nm, which were sharper with the increasing x-value. The optical bandgaps of CuCr1-xO2 films with the pure delafossite-CuCrO2 phase were approximately 3.0 eV. The electrical conductivity of CuCr1-xO2 films with the pure delafossite-CuCrO2 phase was 1.1 x 10(-3) S cm(-1) (x = 0.00), and increased to 0.16 S cm-1 (x = 0.20). The corresponding carrier concentration of CuCr1-xO2 films with the pure delafossite-CuCrO2 phase was 2.8 x 10(14) cm(-3) (x = 0.00), and markedly increased to 1.8 x 10(16) cm(-3) (x = 0.20). The Cr-deficient condition in delafossite-CuCrO2 films enhances film electrical conductivity and carrier concentration, but retains the film's high-visible transparency. (C) 2013 Elsevier B.V. All rights reserved.