Electric-field gradients at Ta donor impurities in Cr2O3(Ta) semiconductor

G. N. DARRIBA; L. A. ERRICO; E. L. MUÑOZ; D. RICHARD; P. D. EVERSHEIM; M. RENTERÍA

PHYSICA B - CONDENSED MATTER

ELSEVIER

Lugar: Amsterdam; Año: 2009 vol. 404 p. 2739 - 2741

0921-4526

We report perturbed-angular-correlation (PAC) experiments on 181Hf(-181Ta)-implanted corundum Cr2O3 powder samples in order to determine the magnitude and symmetry of the electric-field gradient (EFG) tensor at Ta donor impurity sites of this semiconductor. These results are analyzed in the framework of ab initio full-potential augmented-plane wave plus local orbitals (FPAPW+lo) calculations. The results are also compared with EFG results coming from PAC experiments in isomorphous a-Al2O3 and a-Fe2O3 doped with 111In-111Cd and 181Hf-181Ta tracers. This combined analysis enables us to quantify the magnitude of the lattice relaxations induced by the presence of the impurity and to determine the charge state of the impurity donor level introduced by Ta in the band gap of the semiconductor.