Fabrication and field-emission performance of zinc sulfide nanobelt arrays

Large-scale, well-aligned, and oriented wurtzite ZnS nanobelt arrays have been synthesized by a simple template-free solvothermal reaction and subsequent heat-treatment process. The ZnS nanobelts grow along the [0001] direction perpendicularly on a zinc substrate, which have a thickness of about 30 nm, widths of several hundreds of narrometers, and uniform length up to 4,mu m. The selection of Zn foil as the substrate is crucial for the formation of ZnS nanostructured arrays. The concentration of Zn ions, the pH value in the initial precursor solution, and the reaction temperature also have an important influence on the morphology of the final arrays. The formation of the nanobelt arrays are attributed to the structural compatibility of the substrate with ZnS and the growth-rate-dependence of morphology. Importantly, such nanostructured arrays show good field-emission properties with low turn-on fields (3.8 V mu m(-1)) and high field-enhancement factors (1839). This is attributed to the top edges and corners of the free-standing and well-aligned nanobelts, suitable number density of emitters, and good electric contact of the nanobelts with the conducting substrate where they grow. This well-aligned ZnS nanobelt array is expected to be the promising candidate for various field-emission applications, such as flat-panel displays and other vacuum microelectronic devices.