Abstract
The formation process of lattice defects in single crystals of ZnO and their contribution to electric conduction were investigated by means of electric conductivity measurements and positron annihilation lifetime spectroscopy (PALS). For the ZnO samples once heated at high temperatures between 1073 K and 1273 K, we observed defect-induced n-type conductivity by sample warming or light irradiation to the sample, suggesting that interstitial zinc atoms (Zni) and oxygen vacancies (VO) as shallow and deep donors, respectively, were formed by the high-temperature heating. After heat treatment at 1373 K, however, the conductivity arises only from thermal excitation by sample warming, demonstrating that only Zni contributes to the conductivity but VO does not. Based on the above observation and the results of PALS measurements for the samples heated at high temperature, we propose a mechanism of the n-type conduction in ZnO that carrier electrons are provided by interstitial zinc atoms as a result of electron-hole cancellation through interaction between zinc vacancies (VZn) and VO.
Published Version
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