Position-controlled AlN/ZnO coaxial nanotube heterostructure arrays for electron emitter applications.

We studied the fabrication and field-emission characteristics of position-controlled AlN/ZnO nanotube heterostructure arrays. AlN layers with various thicknesses from 20 to 52 nm were deposited coaxially on the position-controlled ZnO nanotube arrays. The field-emission properties of the coaxial AlN/ZnO nanotube arrays were controlled using the AlN thickness and the nanotube interdistance. As compared to the bare ZnO nanotube arrays, the AlN-coated coaxial nanotube arrays exhibited enhanced electron emission, and the optimum AlN coating layer thickness on the nanotube tips was 26 nm. The improved field emission from the coaxial nanotube heterostructures is attributed to the low electron affinity and the thickness modulation effect of the AlN coating layer.

Photocatalysis using GaN nanowires.

The photocatalytic activity of GaN nanowires was investigated for the use of GaN nanowires as photocatalysts in harsh environments. GaN nanowires with diameters of 20-50 nm and lengths of 4-6 microm were prepared by Ni catalyst-assisted metal-organic chemical vapor deposition. Comparisons of GaN nanowires with GaN submicron dot arrays and thin films showed that GaN nanowires exhibit much better photocatalytic activity, resulting from a high surface-to-volume ratio. In addition, GaN nanowires exhibited good ability to photodegrade organic dye at various pHs, even under strong acidity and alkalinity. The photocatalytic activity of GaN nanowires was also compared with that of ZnO and TiO(2) nanowires.