INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
congresos y reuniones científicas
DFT Study of Electric-Field Gradients and Magnetic Fields at Dilute Cd Atoms Doping Al2O3 Near the (001) Surface
G. N. DARRIBA; R. FACCIO; M. RENTERÍA
Congreso; HFI/NQI2014, 5th Joint Meeting of the 17th International Conference on Hyperfine Interactions & 21th International Symposium on Nuclear Quadrupole Interaction; 2014
HFI/NQI Executive Committee
In this work we present an electronic structure calculation study from first principles of Cd atoms located at and near the (001) a-Al2O3 semiconductor surface. In particular, we focus at the origin of the magnetic interaction that appears at Cd impurities located at this surface. For this, we studied the total and partial density of states projected at Cd and their nearest oxygen neighbors, as a function of the depth of the Cd atom from the (001) a-Al2O3 surface. Two methods with different basis set were used: the Full-Potential Augmented Plane Wave plus local orbitals (FP-APW+lo), using the WIEN2k code, and a linear combination of numerical localized atomic orbital basis sets, using the SIESTA code. The Cd impurity is located at Al substitutional sites in the reconstructed a-Al2O3 surface and as a function of the depth from the surface. Besides the appearance of the magnetic interaction, the electric-field gradient (EFG) at the topmost Cd atom at the equilibrium positions in the reconstructed surface is 4 times larger than the EFG at dilute Cd atoms located in bulk, in agreement with the experimental EFG ratio for 111Cd atoms located at the surface and at bulk of metallic indium. Through these comparisons we demonstrated the large sensitivity of 111Cd probe atoms for evaluating surface and bulk properties on Al2O3.