Electronic ferroelectricity in ZnO

Abstract

Novel ferroelectricity in II–VI semiconducting ZnO was studied. The mechanism of ferroelectricity was examined based on size-mismatch model and electronic model. If the ionic size-mismatch between substituted and the host ions is important, the introduction of Be2+ (ionic radius 0.3 Å) may be more effective rather than Li+ (0.60 Å). On the other hand, if the changes in electronic configuration are important, the Mg2+ may play a different role from the isoelectronic Li+ and Be2+. Dielectric measurements indicate that the introduction of Mg2+ instead of Li+ suppresses T c, while isoelectronic Be2+ shows almost the same Tc. This suggests that ZnO is the first ferroelectric with electronic origin.