Electronic properties of bivalent cations (Be, Mg and Ca) substitution for Al in delafossite CuAlO2 semiconductor by first-principles calculations

Electronic properties of delafossite-type CuAlO2 doped with the bivalent cation (Be, Mg or Ca) were systematically calculated by using first-principles PAW method based on density functional theory. The calculated results show the Cu–O distance nearest to the substituted bivalent cation for Al (0.5 0.5 0.5) is decreased with the increase of atomic number from Be to Ca. Moreover, the denser energy band structures have been observed in the valence band in the substituted structures, which are related to the enhancement of covalent character of the Cu–O bond nearest to the substituted site. The contributions from the substituted bivalent cations (Be2+, Mg2+ and Ca2+) to the valence band begin at −6.5 eV, relative to −8 eV of Al3+, which could be another cause to variations in band structures. From Be to Ca, their partial densities of states show the contributions to the valence band are gradually decreased, in great agreement with the variation trend for the pauling electronegativity. The calculated defect formation energies indicate the (BeAl, −1) forms more easily than the others.

► Electronic properties of CuAlO2 substituted with bivalent cations were studied.
► Denser band structures were observed in the substituted CuAlO2.
► The defect (BeAl, −1) forms more easily compared to others.