The mechanism of Al donor defects in (Zn, Co)O:Al: a view from resonant x-rayspectroscopies

Abstract

We studied the effect of Al doping inZn0.94Co0.05Al0.01O nano-powders from the electronic structure point of view by applying x-ray absorptionspectroscopy and resonant inelastic x-ray scattering at the oxygen K- and Co L-edges. Theintensity of the pre-edge structure of the O-K XAS spectra is enhanced following theintroduction of the Al defect. Multiple scattering calculations demonstrate it can beaccounted for by the gain of the hybridization strength between O 2p and Al 3p (and/orCo 3d) states. The consensus on the hybridization strength is reached by combining Co-LXAS and RIXS investigations and multiplet calculations. It reveals different spatialsubstitutions of Al doping can alter the number of shared oxygen atoms between the Coand Al tetrahedrons. These shared ligands are responsible for the Al 3p and Co 3dstate hybridization strength as well as the ferromagnetism of the ground state.The magnetic difference is better understood to be governed by various sharedoxygen atoms rather than the distance between the Al defect and Co impurities.