Influence of Cd impurity on the electronic properties of CuAlO2 delafossite: first-principles calculations

Abstract

We report on first-principles band-structure calculations of the semiconducting CuAlO2 delafossite compound in the pure form and also with Cd impurity occupying either a Cu or Al position. The computational tool was a full-potential linear augmented plane-wave method, with the generalized gradient approximation accounting for the exchange and correlation effects. The changes caused by the presence of Cd are studied by the analysis of the electronic structure and the electric field gradient (EFG) in both Cd-doped and pure CuAlO2 systems. Good agreement between the calculated and measured EFGs at Cd substituting for Cu or Al atoms in CuAlO2 indicates that the calculations were able to correctly describe the ground state of the system containing the impurity. It is shown that a specific hybridization 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-doped system changes its electrical properties when Cd replaces Cu atoms (producing an n-type semiconductor), but not when it substitutes for Al atoms.

Reactive SputteredWide-Bandgap p-Type Semiconducting Spinel AB2O4 and Delafossite ABO2 Thin Films for “Transparent Electronics”

“…Several groups theoretically calculated the effects on the electronic behavior of the material due to the presence of various cations in Cu and/or Al sites. Lalić et al [188][189][190] showed that Cd and Zn substitutions on Cu site would produce n-type conductivity in the material, whereas Ni doping in Cu sites would enhance the p-type conductivity of the material. But Cd doping on Al sites would have no effect on the electrical properties of the material.…”

Correlation between the EFG Values Measured at the Cd Impurity in a Group of Cu-based Delafossites and the Semiconducting Properties of the Latter

“…[4] we presented band-structure calculations for CuAlO 2 compound with an isolated Cd impurity substituting either Cu (Cd Y Cu) or Al (Cd Y Al) atom. In both cases Cd changes interatomic distances in its neighborhood.…”

“…The task was too complicated to be done directly, by performing the calculations for all compounds, since all of them except the CuAlO 2 are anti-ferromagnets with complicated alignments of magnetic moments (a fact which is difficult to treat accurately in the theory). Instead, we achieved the goal indirectly, in three consecutive steps: 1) by analyzing results of our previous theoretical study of doped CuAlO 2 compound [4] which exhibits an elevated EFG when Cd substitutes the Cu site, and performing some additional EFG decompositions; 2) by calculating EFGs in group of molecules constructed in a way which simulate the Cd neighborhood in delafossites; 3) by calculating electronic structure and the EFG in Cd-doped CuCrO 2 compound, which exhibits the smaller EFG at Cd occupying the Cu site. All calculations were performed using the full potential linear augmented plane wave (FP-LAPW) method [5], as embodied in WIEN2k computer code [6].…”

Electronic structure of the n-type doped AgInO2 and CuAlO2 delafossites: similarities and differences

“…This conclusion emerged as a result of series of the first-principles full-potential linear augmented plane wave (FP-LAPW) calculations that we performed for the CuAlO 2 system containing Cd impurities [4], and the Zn or Ni impurities [5] at the Cu position. In this paper we continue to investigate the A site doping effects in the SDOs, but now in their Ag-based branch.…”

“…This band is impurity induced, half filled (one electron), and consists mainly of the Cd s and d z 2 , NN O p z and second NN Cu d states. Since its electron density is widely spread over the crystal [4] (Fig. 2b), the electronic structure displays some relevant differences.…”