Silver migration and trapping in ion implanted ZnO single crystals

Abstract

Articles you may be interested in Effect of implanted species on thermal evolution of ion-induced defects in ZnOPotentially, group-Ib elements (Cu, Ag, and Au) incorporated on Zn sites can be used for p-type doping of ZnO, and in the present paper, we use ion implantation to introduce Ag atoms in wurtzite ZnO single crystals. Monitoring the Li behavior, being a residual impurity in the crystals, as a tracer, we demonstrate that Zn interstitials assist the Ag diffusion and lead to Ag pile-up behind the implanted region after annealing above 800 C. At even higher temperatures, a pronounced Ag loss from the sample surface occurs and concurrently the Ag atoms exhibit a trap-limited diffusion into the crystal bulk with an activation energy of $2.6 eV. The dominant traps are most likely Zn vacancies and substitutional Li atoms, yielding substitutional Ag atoms. In addition, formation of an anomalous multipeak Ag distribution in the implanted near-surface region after annealing can be attributed to local implantation-induced stoichiometry disturbances leading to trapping of the Ag atoms by O and Zn vacancies in the vicinity of the surface and in the end-of-range region, respectively. Published by AIP Publishing. [http://dx.

Defect stabilization and reverse annealing in ZnO implanted with nitrogen at room and cryogenic temperature

“…The Ag profiles display three distinct peaks and a pronounced diffusion shoulder at the level of $2 Â 10 17 cm À3 for depths !1 lm in both the samples. This Ag behavior is consistent with previously published results 33 where the Ag migration into the crystal bulk was attributed to trap-limited diffusion and zinc vacancies as likely trapping sites. In its turn, the two anomalous peaks, located shallower and deeper than the central main one, were attributed to trapping of Ag atoms at open volume defects formed due to local ion-induced stoichiometry perturbations.…”

“…4 in Ref. 33) reveals a considerably enhanced outdiffusion in the co-implanted samples after 1100 C anneal. This holds especially for the co-N(RT) sample where the near-surface and central Ag peaks are substantially reduced relative to those in the co-N(15 K) sample.…”

“…In its turn, the two anomalous peaks, located shallower and deeper than the central main one, were attributed to trapping of Ag atoms at open volume defects formed due to local ion-induced stoichiometry perturbations. 33,34 That is, the near surface ($150 nm) and end-ofrange ($700 nm) peaks are presumably caused by Ag trapping at oxygen and zinc vacancies, respectively. A quantitative comparison of the Ag concentration profiles in the present co-N(RT) and co-N(15 K) samples with those in singly Ag implanted samples (Fig.…”

A predictive modeling study of the impact of chemical doping on the strength of a Ag/ZnO interface

“…15 Unfortunately, Li is found to assist Ag diffusion involving a process in which the Ag atom substitutes for Li on a Zn site. This Li-assisted mechanism agrees well with experimental observations by Azarov et al 33 On the other hand, Bi appears to be a potentially useful dopant which may inhibit Ag diffusion because of its size and also not weaken the interface significantly. Similar nudged elastic band calculations have been performed on Ag diffusion in Bi-doped ZnO, and the energy barrier is found to be 1.35 eV (see Fig.…”

Influence of Fermi level position on vacancy-assisted diffusion of aluminum in zinc oxide

“…Vacancy-assisted impurity diffusion in semiconductors plays a central role in both device processing and fundamental understanding of the defect interplay. This is particularly true for semiconducting oxides like zinc oxide (ZnO) [1][2][3][4][5][6][7][8], where highly conductive n-type crystals (n-ZnO) can be realized by doping with, e.g., Al or Ga [9] and can be used in optoelectronics and photovoltaics. It is known, however, that self-compensation effects arise in highly doped ZnO [10], which pose a limit to the conductivity, although the exact mechanism remains somewhat controversial.…”