###### Abstract  
Compared with other field-emission nanomaterials, 1D ZnO nanomaterials have attracted considerable scientific unique properties--such as high melting point, high thermal and chemical stability, and ambient insensitivity--which means they have promising potential applications as field emitters in harsh environments. This work proposed a water-assisted physical vapor deposition method to prepare various ZnO nanostructures simultaneously on a silicon substrate with one experimental run. Field emission characteristics of the as-grown ZnO nanomaterials were measured and analyzed. Emission-stimulated desorption was proposed and investigated. The gas released under the emission-stimulated desorption effect was measured in the way of monitoring the variation of the pressure. The results show that the slight variation of the pressure has almost no effects on the field-emissions, and field emission properties can be improved with the gases released from the surface of ZnO under the emission-stimulated-desorption effect. Finally, a low turn-on voltage in the range of 0.5-0.9 V/\(\upmu\)m was achieved and a stable emission current was obtained. The ambient insensitivity of ZnO nanomaterials make them possible to be used as field emission cathodes in harsh environments with fluctuating pressure.  
ZnO nanomaterials; field emission; emission-stimulated desorption 2018 8  
1D nanomaterials have garnered the most attention due to their geometric effects. Among 1D nanomaterials, carbon nanotubes (CNTs) have been studied extensively for field emission due to their high aspect ratio. However, besides the geometric effects, there are also several key factors such as thermal stability and ambient insensitivity which have important effects on field emission. ZnO, as an oxide, exhibits a high melting point and stability in harsh environments. 1D ZnO-based nanostructures--like nanowires [7,8], nanoneedles [9,10], nanorods [11], and nanocombs [12]--have been demonstrated to be appropriate as field emitters. ZnO nanomaterials can be synthesized by using the solution-phase method [13] or vapor-phase method [14,15]. Among vapor-phase methods, physical vapor deposition [15] is a low-temperature approach which is widely used. In this work, a water-assisted physical vapor deposition method was proposed and used to prepare various ZnO nanostructures on a silicon substrate with one experimental run. To examine the stability of the ZnO nanomaterials, field emission characteristics were measured two years later. During the field emission process, emission-stimulated desorption would be accompanied. Emission-stimulated desorption is an important process which has effects on the field emission properties. However, there are few reports on the emission-stimulated desorption process, which stimulates our work on the field emission and emission-stimulated desorption of ZnO nanomaterials. The gas released was measured in the way of monitoring the variation of pressure in vacuum chamber. Field emission was enhanced with the gases desorption from the surface of ZnO nanomaterials. Finally, a low turn-on voltage in the range of 0.5-0.9 V/um and a stable emission current were obtained.