Positron annihilation spectroscopy was used to study vacancy defects in ZnO single crystals grown by various methods from both commercial and academic sources. A combination of positron lifetime and Doppler broadening techniques with theoretical calculations permitted the deduction of both the identities and the concentrations of the vacancies. The annihilation characteristics of the Zn and O vacancies were determined by studying electron-irradiated ZnO grown by using the seeded vapor phase technique. The various ZnO samples were grown using the hydrothermal growth method, the seeded vapor-phase technique, growth from the melt (skull-melting) and both conventional and contactless chemical vapor transport. A comparison was made of the vacancy defects and their concentrations in these materials.

Vacancy Defect Distributions in Bulk ZnO Crystals. Tuomisto, F., Look, D.C.: Proceedings of SPIE, 2007, 6474, 647413