Formation of High Concentrations of Isolated Zn Vacancies and Evidence for their Acceptor Levels in ZnO...

Positron annihilation spectra reveal the formation of high concentrations (> 1020 cm-3) of isolated zinc vacancy (VZn) in oxygen-annealed CVT-grown ZnO crystals, while melt and hydrothermally grown ZnO single crystals show only insignificant zinc vacancy creation. Photoluminescence (PL) emission shows a VZn(0/-1) level at ~ 300 -350 meV, and infra-red absorption spectroscopy indicates the presence of an acceptor-related electronic transition with a continuum at ~ 420 meV. Evidence for red PL (~1.7 eV) emission related to the presence of a VZn(-1/2) center was also observed that exhibited a Jahn-Teller distortion.