PAC and ab initio study of structural and electronic properties of 111Cd impurities in SnO2

E. L. MUÑOZ; G. N. DARRIBA; A. W. CARBONARI; L. A. ERRICO; M. RENTERÍA

Villa de Leyva

Simposio; 21st Latin American Symposium on Solid State Physics (SLAFES).; 2013

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In this work, we present an experimental and ab initio study of structural and electronic properties of SnO2 doped with diluted 111Cd impurities, located at substitutional defect free cation sites of this semiconductor. Experimental Electric-Field-Gradient (EFG) tensor results were obtained using the Time-Differential gamma-gamma Perturbed-Angular-Correlations (PAC) technique. The measurements were performed in 111In((EC)-->111Cd)-diffused SnO2 polycrystalline samples, in the 10-1100K temperature range. For all temperatures, the PAC spectra showed well-defined hyperfine interactions. Below 600 K, an strong damping in the PAC signal was apparent, in agreement with the presence of dynamic hyperfine interactions associated with electronic relaxations in the 111Cd environment attributed to the electron capture decay after-effects of 111In. The ab initio calculations were performed applying the Full-Potential Augmented Plane Wave plus local orbitals (FP-APW+lo) method. In these calculations, we used supercells in order to obtain an impurity dilution where the impurity does not sense the effects produced by the presence of their images, in order to reproduce correctly the experimental results. Since the Cd impurity is formally a double acceptor impurity in SnO2 when it replaces a Sn atom, we performed calculations as a function of the Cd charge state, adding until 2 e- to the doped supercell. Based in the predicted charge state dependence of the EFG, we could present an ab initio scenario that allows us to interpret all observed interactions and the phenomenon of after-effects in this impurity-host system.