Experimental and ab initio study of 181Ta-doped Sc2O3 semiconductor

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

Buenos Aires

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

Comite internacional

Trabajo presentado en forma de poster durante la reunion. Recently, experimental and ab initio studies of hyperne interactions in solids has enabled to reinterpret erroneous assignments in previously reported PAC experiments in diluted semiconductor oxides. In particular, ab initio calculations in Ta-doped In2O3 semiconductor were used to reinterpret the hyperne parameters dependence with the bixbyite lattice constant in these sesquioxides and a correct determination of the experimental electric-eld gradients (EFGs) at defect free cation sites. The systems that need a revision of the hyperne parameters are In2O3 and Sc2O3 among others, due to their smaller lattice parameters. In this work, we present ab initio calculations and results of new Perturbed Angular Correlations experiments on the 181Ta-doped Sc2O3 semiconductor. The theoretical calulations were performed at Ta impurities located at both cationic sites C and D of the Sc2O3 structure, using the Augmented Plane Waves + Local Orbital (APW+LO) method in the framework of the Density Functional Theory (DFT), with an impurity dilution of 1:48. We studied the EFGs for dierent charge states of the impurities (neutral cell, and removing 1 and 2 electrons). The PAC experiments were performed at La Plata with the PACAr spectrometer [1] in Sc2O3 polycrystalline pellets implanted with 181Hf (! 181Ta) ions at the ISKP ion accelerator. The samples were thermally annealed in air to eliminate the radiation dammage (at 673 K, 1173 K, 1273 K, and 1373 K, during 1h). The temperature dependence of the EFGs was determined at defect free cation sites C and D in the range 373 K-1173 K. The APW+LO results were found to be in excellent agreement with the new experimental values. Finally, the dependence of the hyperne parameters with the lattice parameter of the bixbyite oxides was revisited. [1] M. Rentera et al., Hyperne Interactions (2008), in press (DOI 10.1007/s10751-008-9706-9).