Field emission from ordered carbon nanotube-ZnO heterojunction arrays

Low operating electric field and stable emission current have been achieved on ordered carbon nanotube (CNT)-ZnO heterojunction arrays. Pyramid-like micropatterns were firstly prepared via capillarity-driven self-assembly from aligned CNT arrays, ZnO nanowires were subsequently grown via vapor-phase transport (VPT) method. Based on the effect of geometrical structure, low turn-on and threshold fields, and stable emission current were obtained. The high aspect ratio of ZnO nanowires leads to the high field enhancement factor. The optimal density of ZnO nanowires and the excellent interconnection between ZnO and CNT are beneficial to avoid the screening effect and improve the current stability.