Semiconductor properties of Cu-based delafossites revealed by an electric field gradient study

Abstract

In this paper we offer an interpretation of the previously observed trend of the electric field gradient (EFG) values measured in a group of semiconducting delafossites CuBO2 (B = Al, Fe, Cr, Nd) at Cd impurities which substitute either Cu or B atoms. Our theoretical study indicates that this EFG trend reveals one of the most subtle details in the electronic spectrum of the compounds, namely whether the impurity states are formed within or out of the band gap. When Cd substitutes the Cu, it exhibits a larger EFG value in CuAlO2 and CuFeO2 than in CuCrO2 and CuNdO2. This occurs because the Cd states form in the first two compounds a shallow band within the gap, but in the second two compounds they do not. When Cd substitutes the B atom it exhibits almost the same EFG in all delafossites. In this case, Cd states are not formed within the gap in any of the compounds. The same interpretation can be applied to the whole family of CuBO2 delafossites, whatever the B atom is. To arrive at these conclusions we analysed and calculated various systems (Cd-doped CuAlO2 and CuCrO2 compounds, and molecular clusters) using the full-potential linear augmented plane wave method.

Effect of Cr substitution on the electronic structure ofCuAl1−xCrxO2

“…14͒ and Cd. 15 Numerous computational and theoretical studies of p-type TCO materials have been published, but in the case of CuAlO 2 these have tended to neglect the underlying chemistry in favor of analyses of the effects of doping on the band structure. [16][17][18][19][20] In CuAlO 2 , the effects of Cu and Al vacancies, and Be, Mg, and Ca dopants, have been investigated using local-density approximation ͑LDA͒-based linearized augmented-plane-wave ͑LAPW͒ calculations.…”

Electronic structure of CuCrO2 thin films grown on Al2O3(001) by oxygen plasma assisted molecular beam epitaxy

“…Mg-doped CuCrO 2 has the highest reported p-type conduction of any TCO. 18 Other divalent dopants such as Ca, 19 Ni, 20 and Cd 21 have also been studied.…”

Preparation of delafossite-type CuCrO2 films by sol–gel method

“…Up to now, the preparation of delafossite structure films has mainly been carried out by pulsed laser deposition (PLD) [22][23][24][25][26] and sputtering [4,12]. Solution methods, such as sol-gel processing, were expected to be an alternative, competitive approach to prepare these conducting oxides.…”