Electric field gradient calculations in ZnO samples implanted with 111-In(111-Cd)
A first-principles study of the electric field gradient (EFG) calculated for ideal and 111In(111Cd) implanted ZnO samples is reported in the present work. The study was made for ZnO ideal hexagonal structures and supercells were introduced in order to consider the possible implantation environments. The calculation was done using the “WIEN2k” code within the density functional theory, the exchange and correlation effects were determined by the GGA approximation. Three possible 111In(111Cd) implantation configurations were studied, one substitutional incorporation at cation site and two interstitials. The obtained EFG values for the ideal structure and the substitutional site are in good agreement with the experimental reports measured by perturbed angular correlation (PAC) and high precision nuclear magnetic resonance (NMR). Thus, the ascription of substitutional incorporation of 111In(111Cd) probe atom at the ZnO cation site after annealing was confirmed.
- [Show abstract] [Hide abstract] ABSTRACT: Local environments in 0.5 at.% In-doped ZnO were investigated by means of the time-differential perturbed angular correlation (TDPAC) method. In a comparative study, using the 111Cd probe nuclei as the decay products of different parents, 111In and 111mCd, we found that 111In microscopically forms a unique structure with nonradioactive In ion(s) dispersed in ZnO, whereas 111mCd has no specific interaction with the In impurities. The spectral damping of the TDPAC spectra is attributed to the aftereffect following the EC decay of 111In. It was demonstrated from the aftereffect that the local density and/or mobility of conduction electrons at the 111In probe site in the In-doped ZnO is lowered due to the characteristic structure locally formed by the dispersed In ion(s).0Comments 4Citations
- [Show abstract] [Hide abstract] ABSTRACT: Local structures in zinc oxide (ZnO) doped with In ions were investigated by means of the time-differential perturbed angular correlation (TDPAC) method with the Cd-111(a dagger In-111) probe. Indium-concentration dependence of the TDPAC spectra suggests that the local structures formed by the impurities are sensitive to their population in the system: In ions occupy defect-free Zn sites when doped with a trace amount; they locally form microscopic unique structures widely dispersed in ZnO at 0.05 at. % or higher; and other compounds are formed at the In concentration as high as 10 at. %. Their characteristic structures are discussed based on the hyperfine-interaction parameters.0Comments 0Citations
- [Show abstract] [Hide abstract] ABSTRACT: The stability of locally-associated Al and In impurities in zinc oxide (ZnO) was investigated by means of the time-differential perturbed angular correlation (TDPAC) method with the 111Cd(←111In) probe. We found that Al and In impurities associate with each other by their thermal diffusion in air, and the association process irreversibly proceeds at high temperature. In vacuum, however, it was revealed that the rigid bonding between Al and In ions dissociates by heat treatment at temperatures higher than 873 K, and this dissociation process is enhanced with increasing annealing temperature. The contrastive atmosphere dependence of the stability of the association between Al and In in ZnO is discussed based on the variation of the TDPAC spectra against heat-treatment temperature.0Comments 0Citations