INVESTIGADORES
RENTERIA Mario
congresos y reuniones científicas
Título:
Ab initio study of structural and electronic properties of Ta impurities in SnO2
Autor/es:
GERMÁN NICOLÁS DARRIBA; EMILIANO LUIS MUÑOZ; LEONARDO A. ERRICO; MARIO RENTERÍA
Lugar:
Villa de Leyva
Reunión:
Simposio; SLAFES 2013; 2013
Institución organizadora:
SLAFES
Resumen:
In this work, we present ab initio
calculations of structural and electronic properties of Ta impurities, located
at substitutional cation sites of the SnO2 semiconductor. The
calculations were performed, in the framework of the Density Functional Theory,
using the WIEN2k code implementation of the Full-Potential Augmented Plane Wave
plus local orbitals (FP-APW+lo) method. The results obtained for the electric-field-gradient
tensor (EFG) are here compared with experimental results obtained using the
Time-Differential Perturbed-Angular-Correlations technique (TDPAC). We used
2x2x3 supercells in order to obtain the correct impurity dilution, and since Ta
is a single donor impurity in SnO2, we performed the ab initio calculations for two-charge
state: neutral and charged. Ta introduces an impurity level
in the gap region at the bottom of the conduction band, which is partially
filled in the neutral and empty in
the charged charge state,
respectively. Ta produces contractions in Ta-O distances, and these relaxations
try to reconstruct the neighborhood of
Ta-O in Ta2O5. After structural relaxations, the ab initio calculations provided almost the
same EFG for both charge states, since the removed electron is not localized at
the Ta atom and the final oxygen positions are similar. Finally, comparing the
TDPAC results, the predicted EFG and
formation energy calculations, we showed that the 181Ta impurities
are located at substitutional defect ?free Sn sites in the SnO2 host
lattice, being the impurity already ionized at RT.