Formation of high concentrations of isolated Zn vacancies and evidence for their acceptor levels in ZnO

Title
Formation of high concentrations of isolated Zn vacancies and evidence for their acceptor levels in ZnO
Authors
최지원나렌드라 싱Lynn A. BoatnerMatthew D. McCluskeyKelvin G. Lynn
Keywords
Positron annihilation spectroscopy; PL; ZnO; XPS; Zn vacancy; SEM; Acceptor level; FTIR
Issue Date
2017-12
Publisher
Journal of alloys and compounds
Citation
VOL 729-1037
Abstract
Research is described here that is directed toward obtaining p-type ZnO crystals either by doping or by creating native defects. Theoretically, zinc vacancies are shallow acceptors that should allow for p-type conduction. Bulk ZnO crystals can be grown by chemical vapor transport (CVT), melt solidification, and hydrothermal methods. Here we have explored annealing processes with the goal of creating zinc vacancies in bulk ZnO crystals. Positron annihilation spectra reveal the reproducible formation of high concentrations (>1020 cm− 3) of isolated zinc vacancies (VZn) in oxygen-annealed, CVT-grown ZnO crystals in the ∼100– 150 nm near-surface. Melt- and hydrothermally grown samples, in contrast, show insignificant levels of zinc vacancy creation. Photoluminescence (PL) emission spectra indicate a VZn(0/-1) acceptor level at ∼ 155– 165 meV; red PL (∼1.7 eV) emission, related to the VZn(-1/-2) level, was also observed. Infrared absorption spectroscopy reveals the presence of a zinc vacancy complex with a hole binding energy range of 420– 450 meV – and with a continuum suggesting a p-type region. XPS measurements support the deficiency of Zn after oxygen annealing the CVT-grown ZnO single crystal.
URI
http://pubs.kist.re.kr/handle/201004/66337
ISSN
0925-8388
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