Properties Of Bulk ZnO Research Articles

Oxygen vacancy in ZnO-w phase: pseudohybrid Hubbard density functional study

The study of zinc oxide, within the homogeneous electron gas approximation, results in overhybridization of zinc 3d shell with oxygen 2p shell, a problem shown for most transition metal chalcogenides. This problem can be partially overcome by using LDA + U (or, GGA + U) methodology. However, in contrast to the zinc 3d orbital, Hubbard type correction is typically excluded for the oxygen 2p orbital. In this work, we provide results of electronic structure calculations of an oxygen vacancy in ZnO supercell from ab initio perspective, with two Hubbard type corrections, UZn-3d and UO-2p. The results of our numerical simulations clearly reveal that the account of UO-2p has a significant impact on the properties of bulk ZnO, in particular the relaxed lattice constants, effective mass of charge carriers as well as the bandgap. For a set of validated values of UZn-3d and UO-2p we demonstrate the appearance of a localized state associated with the oxygen vacancy positioned in the bandgap of the ZnO supercell. Our numerical findings suggest that the defect state is characterized by the highest overlap with the conduction band states as obtained in the calculations with no Hubbard-type correction included. We argue that the electronic density of the defect state is primarily determined by Zn atoms closest to the vacancy.

Optical study of bulk ZnO for strong coupling observation in ZnO-based microcavities

We report an experimental study of the excitonic properties of bulk ZnO and the strong coupling observation in hybrid ZnO-based microcavities. The strong coupling is highlighted with a Rabi splitting value of about 70 meV. The influence of the excitonic and band-to-band absorptions on the observation of this strong light-matter coupling regime is analysed through the evolution of the reflectivity spectra obtained on microcavities with different active layer thicknesses.