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Title: Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (V{sub Zn} − Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of V{sub Zn} compared to V{sub O}, more V{sub Zn}-abundant clusters are formed than V{sub O}-abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (V{sub Zn} − Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to V{sub O} donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)
  2. Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of)
  3. (Korea, Republic of)
  4. Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Busan 609-735 (Korea, Republic of)
  5. Pacific Northwest National Laboratory, MS K8-93, P.O. Box 999, Richland, Washington 99352 (United States)
Publication Date:
OSTI Identifier:
22303851
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 25; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; ANNIHILATION; COMPUTERIZED SIMULATION; CRYSTAL DEFECTS; DIFFUSION BARRIERS; DISSOCIATION ENERGY; EQUILIBRIUM; EV RANGE; MONTE CARLO METHOD; POSITRONS; SPECTROSCOPY; VACANCIES; ZINC OXIDES