Effect of Cr substitution on the electronic structure ofCuAl1−xCrxO2

Abstract

The geometries and electronic structures of CuAl 1−x Cr x O 2 have been investigated using density-functional theory with on-site corrections for strongly correlated systems ͑GGA+ U͒ for x =0, 1 2 , 1. Al is found to be well described within the ionic model, with a valence charge corresponding to a +3 oxidation state. Substituting Cr for Al is predicted to increase the density of states at the top of the valence band, in agreement with experimental x-ray photoemission spectroscopy data. Analysis of atom-projected densities of states and valence charges suggests that this is due to increased covalency between Cr and O; the valence charge for O in the Cu-O-͑Al,Cr͒ subunits changes from −1.74 to ϳ−1.25 when Cr replaces Al. This produces an indirect oxygenmediated change to the Cu d states.

Band structure calculations of CuAlO2, CuGaO2, CuInO2, and CuCrOGillen1, Robertson2 2011Phys. Rev. B

“…We find the peak maximum at about 3.1 eV and an additional shoulder at about 2.9-3 eV below the VBM. Interestingly, this agrees well with recent x-ray photoelectron spectroscopy XPS experiments 27,28 , where the peak maximum was found at an energy of -2.8 to -3 eV. The good prediction of the depth of d levels from sX-LDA was previously shown for ZnO and other transition-metal semiconductors 29,30 .…”

“…Another direct band gap occurs at the F and is 3.25 eV wide. Scanlon et al 28 report a value of 2.04 eV for the fundamental (indirect) gap, but find a larger difference between indirect and direct gap due to the comparatively weak pushdown of the Cu d states in their calculations. Table III summarizes the obtained band gap sizes.…”

Atomistic simulations of copper oxidation and Cu/Cu2O interfaces using charge-optimized many-body potentials

“…62 The effect cannot be modeled with current DFT implementations. 57 Classical potentials have had better success in replicating the effect where, the Cu 2+ cation is modeled as an aspherical ion with a distorted neighbor shell. 62 This special feature of Cu 2+ cation has also been shown to pose an effect to the Jahn-Teller distortion of [Cu(OH 2 ) 6 ] 2+ molecules.…”

Understanding doping anomalies in degenerate p-type semiconductor LaCuOSe

“…Hosono and co-workers then exploited the design principles that emerged from this study, subsequently called "Chemical Modulation of the Valence Band" (CMVB) to show that other Cu I based oxides were also p-type TCOs, e.g. delafossite structured CuMO 2 , (M ¼ Cr, B, Sc, Y, In, Ga) [17][18][19][20][21][22][23][24] and SrCu 2 O 2 .…”