Bulk, interface and surface properties of zinc oxide

Zinc oxide (ZnO) is a highly developed oxide semiconductor that has been widely employed in industry as varistor ceramics, transparent conductor films, surface acoustic wave resonators, and so on. However, many questions about its fundamental properties remain unanswered. For instance, density functional theory simulations are currently contradicting the common conception established by many experimental scientists that non-stoichiometry is the primary factor inducing the native conductivity of ZnO. Thus, it may be necessary to reconstruct the conceptual models of the solid-state chemistry and physics of oxide semiconductors. In this context, this paper gathers the knowledge and suggestions presented in previous studies and attempts to find directions for the next steps in further scientific and technological development of ZnO-related materials and structures. (C) 2014 The Ceramic Society of Japan. All rights reserved.