Enhanced field emission from ZnO nanorods via thermal annealing in oxygen

To optimize the field emission behavior of the ZnO nanorods, postthermal annealing in different ambience was conducted. The field emission properties of the ZnO nanorods are considerably improved after annealing in oxygen and getting worse when annealing in air or ammonia. Photoluminescence and Raman spectroscopy were employed to elucidate the reason for such a significant improvement of the field emission when annealing in oxygen. Those detailed analyses suggested that oxygen annealing can reduce the oxygen vacancy concentration, improve the crystal quality, lower the work function, and increase the conductivity of the ZnO nanorods. Our work is important for applications of ZnO nanorods as a promising candidate in flat panel displays and high brightness electron sources.