Ionic exchange of Hf donor impurities in the wide-gap semiconductor Tm2O3

The ionic exchange of Hf donor impurities in substitutional cationic sites of the cubic (bixbyite) phase of the wide-gap semiconductor Tm2O3 was studied. The doping process was performed by ball-milling-assisted solid-state reaction of Tm2O3 and neutron-activated m-HfO2. 181Ta atoms, obtained by the β-decay of the 181Hf-isotope, were used as probes in time-differential perturbed-angular-correlation (TDPAC) experiments carried out after each step of the doping process. The measured hyperfine interactions at 181Ta sites enabled the electric-field gradient (EFG) characterization at representative Hf impurity sites of each step of the process. The efficiency and substitutional character of the exchange process is discussed and elucidated in the framework of an empirical EFG systematic established in isostructural rare-earth bixbyite sesquioxides.