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; International Workshop "At the Frontiers of Condensed Matter Physics IV"; 2008

Comité Internacional

<!-- /* Font Definitions */ @font-face {font-family:"CG Times"; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-alt:"Times New Roman"; mso-font-charset:0; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:3 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:none; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; layout-grid-mode:line;} p.MsoBodyText2, li.MsoBodyText2, div.MsoBodyText2 {margin:0cm; margin-bottom:.0001pt; text-align:justify; mso-pagination:none; font-size:10.0pt; font-family:"CG Times"; mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman"; layout-grid-mode:line;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> In this work we report Perturbed-Angular- Correlation (PAC) experiments on 181Hf/181Ta implanted corundum Cr2O3 policrystals determiningthe magnitude and symmetry of the Electric-Field Gradient tensor (EFG). The measurements were carried out at 333 K after each step of a series of thermal annealings in air in the range 673{1273 K performed in order to obtain the maximum substitution of the Hf impurities at defect free Cr sites in the semiconductorcrystal structure. These results are analyzed in terms of self-consistent electronic structure FP-LAPW calculations in the dilute (1:4) Cr2O3:Ta system using the WIEN2k code.The calculations were carried out for diverse charge states of the impurities and are compared whit PCM calculations and with the EFG results coming from the PAC experiments using both 111In/111Cd and 181Hf/181Ta traces in the isomorphous -Al2O3, - Fe2O3 and Cr2O3 semiconductors.This combined study enables the determination of lattice relaxations induced by the presence of impurities in the host and the charge state of the impurity donor level (Ta 5d) introduced in the band gap of the semiconductor.