PNNL

Abstract

We report the use of controlled introduction and removal of Zni to test the hypothesis that high-Curie-temperature ferromagnetism in cobalt-doped ZnO (Co2+:ZnO) is mediated by carriers. Using oriented epitaxial Co2+:ZnO films grown by chemical vapor deposition, kinetics measurements were used to correlate the oxidative quenching of ferromagnetism with the diffusion and oxidation of interstitial zinc. These results demonstrate controlled systematic variation of a key parameter involved in the ferromagnetism of Co2+:ZnO, namely interstitial zinc, and in the process unambiguously reveal this ferromagnetism to be dependent upon carriers. The distinction between defect-bound and free carriers in Co2+:ZnO is discussed