Hydrothermal growth and field emission properties of ZnO nanotube arrays

Highly aligned ZnO nanotube array films on the conducting substrates have been synthesized by a simple hydrothermal method. The as-synthesized ZnO nanotubes have diameters of 300–400nm and lengths of 7μm (the aspect ratios of ~20). The field emission of ZnO nanotube array films shows a turn-on field of about 4.6V/μm at a current density of 1μA/cm and emission current density up to about 0.22mA/cm
²
at a bias field of 8.25 V/μm. These result suggest that the relatively low the aspect ratios of the ZnO nanotue can posses strong field emission characteristics.