Electric-field gradient characterization at 181Ta impurieties in sapphire single crystals

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

PHYSICA STATUS SOLIDI B-BASIC RESEARCH

WILEY-VCH

Lugar: Weinheim; Año: 2005 vol. 242 p. 1928 - 1932

0370-1972

We report Perturbed-Angular-Correlation (PAC) experiments on corundum Al2O3 single crystals implanted with 181Hf/181Ta ions at the ISKP at Bonn and measured at La Plata with high efficiency and time resolution. The magnitude, asymmetry, and orientation (with respect to the crystalline axes) of the electric-field gradient (EFG) tensor were determined measuring the spin-rotation curves as a function of different orientations of the single crystals relative to the detector system. These results are analyzed in the framework of point-charge model and ab initio Full-Potential Linearized-Augmented Plane Wave calculations, and compared with EFG results coming from PAC experiments with 111In/111Cd impurities. This combined study enables the determination of lattice relaxations induced by the presence of the impurity and the state of charge of a deep impurity donor level in the band gap of the semiconductor.