Influenceof Cd impurity on the electronic properties of CuAlO2delafossite: first-principles calculations

Abstract

We report on first-principles band-structure calculations of thesemiconducting CuAlO2 delafossite compound in the pure formand also with Cd impurity occupying either a Cu or Alposition. The computational tool was a full-potential linearaugmented plane-wave method, with the generalized gradientapproximation accounting for the exchange and correlationeffects. The changes caused by the presence of Cd are studied bythe analysis of the electronic structure and the electric fieldgradient (EFG) in both Cd-doped and pure CuAlO2 systems. Goodagreement between the calculated and measured EFGs at Cdsubstituting for Cu or Al atoms in CuAlO2 indicates that thecalculations were able to correctly describe the ground state ofthe system containing the impurity. It is shown that a specifichybridization scheme, involving Cu (and Cd) s and dz2 orbitals and neighbouring O pz orbitals,takes place at the Cu sites in CuAlO2 as proposed earlier.The results of the calculations indicate that the Cd-dopedsystem changes its electrical properties when Cd replaces Cuatoms (producing an n-type semiconductor), but not when itsubstitutes for Al atoms.