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Crystal TaS2 nanobelt arrays were fabricated on Ta wafers by a two-step method. Field-emission measurements show that the nanobelt arrays are decent field emitters with a turn-on field of approximately 0.7 V microm(-1), a threshold field of approximately 2.1 V microm(-1), and a field enhancement factor of approximately 4.33 x 10(4).

NbN nanobelt arrays were prepared by an in-situ conversion of aligned NbS3 nanobelts in the flowing NH3 at 950 degrees C, meanwhile, NbS2 nanobelt arrays were produced by a pyrolysis of aligned NbS3 nanobelts in the flowing argon atmosphere. The morphology and size of those nanobelts are close to the NbS3 nanobelt precursors, having a reactangular section of about 11 x 250 - 520 x 3100 nm2, and a length of about 120 microm. The microstructures were characterized by high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDX). Magnetic measurements showed that the NbN nanobelts have superconductivity below 14.1 K. Field-emission experiments showed that the turn-on and threshold fields of the NbN nanobelt arrays (which are defined to be the macroscopic field to produce a current density of 10 microA/cm2 and 1 mA/cm2, respectively) are 0.61 and 2.3 V/microm, respectively, whereas the turn-on and threshold fields of the NbS2 nanobelt arrays are 0.61 and 3.5 V/microm, respectively, suggesting that they are decent field emitters.

Single-crystalline NbTe 4 microcone, microplate, and nanorod arrays were grown on Nb substrates by a surface-assisted chemical-vapor-transport under different conditions. The microcones are composed of small and large cones with a bending top. The small cones have a top diameter of about 0.2 mm, a bottom diameter of about 1.2 mm, and a length up to approx. 7.7 mm. The large cones originate from self-assembled small cones. The microplates mostly stand on Nb foils, with a diameter of about 2-3 mm and a thickness from 50 to 250 nm. The nanorods have a rectangle section of 250 Â 150 to 250 Â 250 nm 2 or a triangle section with a side of about 250 nm, and a length up to 4.5 mm, partly standing on the substrates. Their growth mechanisms are briefly discussed. Field-emission experiments showed that the three micro/nanostructures have a notable emission current, and their turn-on fields (defined as the electric field required to produce a current density of 10 mA cm À2 ) are 4.7, 2.0, and 1.9 V mm À1 , respectively, suggesting their potential application in electron emission devices.