Experimental and ab initio study of the EFG at donor impurities in the Cr2O3:Ta semiconductor

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

Ciudad Autónoma de Buenos Aires, Argentina

Workshop; Workshop "At the Frontiers of Condensed Matter physics IV"; 2008

Comite internacional

In this work we report Perturbed-Angular-Correlation (PAC) experiments on 181Hf/181Taimplantedcorundum Cr2O3 policrystals determiningthe magnitude and symmetry of the Electric-FieldGradient tensor (EFG). The measurements were carriedout at 333 K after each step of a series of thermalannealings in air in the range 673{1273 K performedin order to obtain the maximum substitution of the Hfimpurities at defect free Cr sites in the semiconductorcrystal structure.These results are analyzed in terms of self-consistentelectronic structure FP-LAPW calculations in the dilute(1:4) Cr2O3:Ta system using the WIEN2k code.The calculations were carried out for diverse chargestates of the impurities and are compared whit PCMcalculations and with the EFG results coming fromthe PAC experiments using both 111In/111Cd and181Hf/181Ta traces in the isomorphous -Al2O3, -Fe2O3 and Cr2O3 semiconductors.This combined study enables the determination oflattice relaxations induced by the presence of impuritiesin the host and the charge state of the impuritydonor level (Ta 5d) introduced in the band gap of thesemiconductor.