NbN and NbS2 nanobelt arrays: in-situ conversion preparation and field-emission performance.

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.