Journal of Physical Studies 23(2), Article 2702 [6 pages] (2019)
DOI: https://doi.org/10.30970/jps.23.2702 DFT STUDY OF NATIVE POINT DEFECTS IN (ZnO)n (n = 34, 60) NANOCLUSTERSR. V. Bovhyra1, O. V. Bovgyra2, D. I. Popovych1, A. S. Serednytsky1
1Pidstryhach Institute for Applied Problems of Mechanics and Mathematics NAS Ukraine, |
Density-functional theory studies within the GGA+U approach of the structural and electronic properties of (ZnO)$_n$ ($n$=34, 60) nanoclusters with native point defects (zinc vacancy (V$_\emph{\emph{Zn}}$), oxygen vacancy (V$_\emph{\emph{O}}$), zinc antisite (Zn$_\emph{\emph{O}}$), and, finally, oxygen antisite (O$_\emph{\emph{Zn}}$)) were performed. The optimization of the structure geometry, as well as the band structure research, was performed. The values for the formation energy, HOMO-LUMO gap, and the partial density of states for each cluster were investigated to establish the influence of the defects on the electronic properties of the (ZnO)$_n$nanoclusters.
It was determined that the most favorable defects of the clustersХ structure were Zn and O vacancies. A zinc vacancy introduces partially occupied states into the bandgap close to the HOMO state of the cluster. These states explain the acceptor behavior of V$_\emph{\emph{Zn}}$ in ZnO. It has two deep acceptor levels above HOMO with values 1.2 and 2 eV. This particular defect has the lowest formation energy value among all acceptor-type defects. An oxygen vacancy is a deep donor type of defect with the lowest formation energy values among all donor type defects. In our case of neutral-type defects, V$_\emph{\emph{O}}$ induces one deep and localized one-electron state into the bandgap. A zinc antisite defect generates both deep and shallow donor levels. It has a very high formation energy and can be treated as a complex of both the oxygen vacancy and zinc interstitial defects. The oxygen antisite is an acceptor-type defect with very high formation energy.
PACS number(s): 73.22.-f, 73.20.At, 61.72.Ww