Field emission from zinc oxide nanoneedles on plastic substrates

The electron field emission from zinc oxide (ZnO) nanoneedles on flexible plastic substrates is reported. ZnO thin films were first deposited on plastic substrates at 200 degrees C using a filtered cathodic vacuum arc technique; the films were then bombarded by Ar+ ion. After ion beam irradiation, high-density ZnO nanoneedle arrays were selectively formed on the thin films. The average diameter and length of the ZnO nanoneedles is around 100 and 700 nm respectively. Field emission measurement showed a fairly low threshold voltage of 4.1 V mu m(-1) with a current density of I mu A cm(-2). The emission current density can be as high as 1 mA cm(-2) at 9.6 V mu m(-1). The result establishes a method of fabricating a flexible field emitter, which should find practical applications in vacuum electronic devices.