Observation of Zn vacancies in ZnO grown by chemical vapor transport

Abstract

We have used positron annihilation spectroscopy to study the vacancy defects in ZnO crystals grown by both the conventional and contactless chemical vapor transport (CVT and CCVT). Our results show that Zn vacancies or Zn vacancy related defects are present in as-grown ZnO, irrespective of the growth method. Zn vacancies are observed in CVT-grown undoped ZnO and (Zn,Mn)O. The Zn vacancies present in undoped CCVT-ZnO are the dominant negatively charged point defect in the material. Doping the material with As introduces also Zn vacancy-related defect complexes with larger open volume.

Investigation of native defects and property of bulk ZnO single crystal grown by a closed chemical vapor transport method

“…Thus, isolated Zn I is unlikely to exist in the annealed ZnO. Positron annihilation lifetime studies have confirmed the existence of both Zn and O vacancies in CVT grown ZnO [37][38][39]. Our combination results of XRD and PL suggest that O V is possibly trapped at the grain boundary in the ZnO sample with poor lattice perfection.…”

Strong violet luminescence from ZnO nanocrystals grown by the low-temperature chemical solution deposition

“…However, after annealing, the violet PL band decreased in intensity but it did not vanish completely. Tuomisto et al [44] confirmed by positron annihilation spectroscopy that the concentration of V Zn -or V Znrelated complexes is sufficiently high (410 16 cm À3 ) in the ZnO crystals grown both the zinc-rich and oxygen-rich conditions. Chen et al have also observed V Zn -related defects in hydrothermal grown ZnO crystals by positron annihilation spectroscopy and found that they can be removed by annealing above 600 1C [45].…”

Vacancy defects in (Zn, Mn)O

“…It has an average value of τ 2 = 230 ± 15 ps. As in our earlier work on the as-grown samples [6], this component can be attributed to positrons annihilating as trapped at Zn vacancies [4,5].…”