Positron annihilation spectroscopy was used to study vacancy defects in crystals grown by using conventional or contactless chemical vapor transport. The results showed that Zn vacancies or Zn vacancy-related defects were present in as-grown ZnO; regardless of the growth method. Zinc vacancies were observed in conventional chemical vapor transport-grown undoped ZnO and (Zn,Mn)O. The Zn vacancies present in undoped contactless chemical vapor transport ZnO were the predominant negatively charged point defect. Doping the material with As also introduced Zn vacancy-related defect complexes with larger open volumes.

Observation of Zn Vacancies in ZnO Grown by Chemical Vapor Transport. Tuomisto, F., Saarinen, K., Grasza, K., Mycielski, A.: Physica Status Solidi B, 2006, 243[4], 794-8