DARRIBA German Nicolas
Experimental TDPAC and Theoretical DFT Study of Structural, Electronic, and Hyperfine Properties in (111In → )111Cd-Doped SnO2 Semiconductor: Ab Initio Modeling of the Electron-Capture-Decay After-Effects Phenomenon
G. N. DARRIBA; E. L. MUÑOZ; A.W. CARBONARI; M. RENTERÍA
JOURNAL OF PHYSICAL CHEMISTRY C
AMER CHEMICAL SOC
Lugar: Washington; Año: 2018 vol. 122 p. 17423 - 17436
In this paper we investigate the effect of Cd doping atultralow concentrations in SnO2 both experimentally, by measuringthe temperature dependence of the electric quadrupole hyperfineinteractions with time-differential γ−γ perturbed angular correlation(TDPAC) spectroscopy using 111Cd as probe nuclei, andtheoretically, by performing first-principles calculations based onthe density functional theory. TDPAC spectra were successfullyanalyzed with a time-dependent on−of f model for the perturbationfactor. These results show combined dynamic plus static interactionswhose electric-field-gradients were associated in this model todifferent stable electronic configurations close to the Cd atoms.The dynamic regime is then originated in fast fluctuations betweenthese different electronic configurations. First-principles calculationresults show that the Cd impurity introduces a double acceptor level in the top of the valence band of the doped semiconductorand produces isotropic outward relaxations of the nearest oxygen neighbors. The variation of the calculated electric-fieldgradient tensor as a function of the charge state of the Cd impurity level shows an interesting behavior that explains theexperimental results, giving strong support from first-principles to the electron-capture af ter-ef fects proposed scenario. Theelectron-capture decay of the parent 111In to 111Cd as well as the double acceptor character of the 111Cd impurity and theelectric nature of the host are shown to contribute to the existence of these types of time-dependent hyperfine interactions.