Electric-field gradients at Ta Donor Impurities in Cr2O3(Ta) Semiconductor

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

PHYSICA B - CONDENSED MATTER

Elsevier

Lugar: Amsterdam; Año: 2009 vol. 404 p. 2739 - 2741

0921-4526

We  report  Perturbed-Angular-Correlation  (PAC)  experiments  on  181Hf (->181Ta)-implanted  corundum  Cr2O3  powder  samples in order to determine the magnitude and symmetry of the electric-field  gradient (EFG) tensor at Ta donor impurity sites of this  semiconductor.  These  results  are  analyzed  in  the  framework  of  ab  initio  Full-Potential  Augmented-Plane  Waves  plus  Local Orbitals  (FP-APW+lo)  calculations.  The  results  are  also  compared  with  EFG  results  coming   from  PAC  experiments  in isomorphous  alpha-Al2O3  and  alpha-Fe2O3   doped  with  111In/111 Cd  and  181Hf/181 Ta  tracers.  This  combined  analysis  enables  us  to quantify the magnitude of the lattice relaxations induced  by the presence of the impurity and to determine the charge state of  the impurity donor level introduced  by Ta in the  band gap of the semiconductor.