The correlation between the p-type hole conduction and the electronic structures of Cr-deficient CuCr1−xO2(x = 0−0.1) compounds was investigated using O K-, Cu, and Cr L3,2-edge x-ray absorption near-edge structure(XANES), scanning photoelectron microscopy, and x-ray emission spectroscopy measurements. XANES spectra reveal a gradual increase in the Cu valence from Cu1+ to Cu2+ with increasing Cr deficiency x, whereas, the
valence of Cr remains constant as Cr3+. These results indicate that the p-type conductivity in the CuCr1−xO2
samples is enhanced by a Cu1+-O-Cu2+ rather than a Cr3+-Cr4+ or direct Cu1+-Cu2+ hole mechanism. Remarkable
Cr-deficiency-induced changes in the densities of Cu 3d, Cu 3d-O 2p, and O 2p states at or near the valence-band
maximum or the Fermi level were also observed. In addition, a crossover of conduction mechanism from thermally
activated (TA) hopping to a combination of TA and Mott’s three-dimensional variable range hopping occurs
around 250 K.
