The room-temperature positron annihilation lifetime for single crystalline ZnO was measured as 164ps. The single component lifetime value was very close to but higher than the theoretically predicted value of ~54ps. Photoluminescence study (at 10K) indicated the presence of hydrogen and other defects, mainly acceptor related, in the crystal. Defects related to a lower open volume than zinc vacancies, presumably a complex with two hydrogen atoms, were the major trapping sites in the sample. The bulk positron lifetime in ZnO was expected to be a little less than 164ps.

Positron Annihilation Lifetime and Photoluminescence Studies on Single Crystalline ZnO. Sarkar, A., Chakrabarti, M., Ray, S.K., Bhowmick, D., Sanyal, D.: Journal of Physics - Condensed Matter, 2011, 23[15], 155801