Abstract Single crystalline tungsten oxides in a form of W5O14 and W18O49 nanowires were synthesized by iodine transport method. The morphology, work functions and field emission properties of these nanowires were investigated. Work functions of the W5O14 (4.20–4.34 eV) and W18O49 (4.55–4.57 eV) nanowires (NWs) have been measured by Kelvin probe force microscopy (KPFM) in ultra-high vacuum. Field emission (FE) measurements of individual nanowires were performed in ultra-high vacuum at microscopic and macroscopic distances between the emitter and electron collector. The obtained FE curves at microscopic distances were analyzed in the framework of the Fowler–Nordheim (F–N) theory. Field enhancement factors of W5O14 at the emitter-collector distance of 2, 4 and 5 μm were calculated to be 110 ± 10, 180 ± 25 and 210 ± 30, respectively, and 125 ± 15 for W18O49 at 2 μm. At macroscopic distances, the F–N theory revealed unrealistic high field enhancement factors: for W5O14 at 1 mm it was 17,000 ± 500, and for W18O49, the field enhancement factors were 5050 ± 30 and 6450 ± 30 at 600 μm and 800 μm emitter-collector distance, respectively. Therefore, more realistic model was discussed. The lower work function and typically smaller diameter of the W5O14 nanowires in comparison with the W18O49 wires, range the W5O14 nanowires to the promising sources of electrons in field emission devices.

中文翻译：

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单晶 W5O14 和 W18O49 纳米线的场发射特性

摘要 通过碘传输法合成了W5O14 和W18O49 纳米线形式的单晶氧化钨。研究了这些纳米线的形态、功函数和场发射特性。W5O14 (4.20–4.34 eV) 和 W18O49 (4.55–4.57 eV) 纳米线 (NW) 的功函数已通过开尔文探针力显微镜 (KPFM) 在超高真空中测量。单个纳米线的场发射 (FE) 测量在超高真空中以发射极和电子收集器之间的微观和宏观距离进行。在 Fowler-Nordheim (F-N) 理论的框架内分析了在微观距离处获得的 FE 曲线。W5O14 在发射极-集电极距离为 2、4 和 5 μm 处的场增强因子分别计算为 110±10、180±25 和 210±30，W18O49 在 2 μm 时为 125 ± 15。在宏观距离上，F-N 理论揭示了不切实际的高场增强因子：对于 1 mm 的 W5O14 为 17,000 ± 500，对于 W18O49，在 600 μm 和 800 μm 发射器处的场增强因子为 5050 ± 30 和 6450 ± 30 - 收集器距离，分别。因此，讨论了更现实的模型。与 W18O49 线相比，W5O14 纳米线具有较低的功函数和通常较小的直径，使 W5O14 纳米线成为场发射器件中很有前途的电子源。讨论了更现实的模型。与 W18O49 线相比，W5O14 纳米线具有较低的功函数和通常较小的直径，使 W5O14 纳米线成为场发射器件中很有前途的电子源。讨论了更现实的模型。与 W18O49 线相比，W5O14 纳米线具有较低的功函数和通常较小的直径，使 W5O14 纳米线成为场发射器件中很有前途的电子源。