Synthesis of\nArrayed Tungsten Disulfide Nanotubes

Tungsten disulfide nanotubes (WS<sub>2</sub>-NTs), with\ntheir cylindrical\nstructure composed of rolled WS<sub>2</sub> sheets, have attracted\nmuch interest because of their unique physical properties reflecting\nquasi-one-dimensional chiral structures. They exhibit a semiconducting\nelectronic structure regardless of their chirality, and various semiconducting\nand optoelectronic device applications have been demonstrated. The\ndevelopment of techniques to fabricate arrayed WS<sub>2</sub>-NTs\nis crucial to realizing the highest device performance. Since the\ndiscovery of WS<sub>2</sub>-NTs, various synthesis techniques have\nbeen reported; however, horizontally arrayed WS<sub>2</sub>-NTs have\nnever been successfully synthesized. Here, we demonstrate a simple\ntechnique to synthesize arrayed WS<sub>2</sub>-NTs. Through precise\ntemperature and gas control, W<sub>18</sub>O<sub>49</sub> nanowires\nare grown along the [1̅101] direction on an r-plane sapphire\nsubstrate, and the nanowires are converted into nanotubes via sulfurization\nunder optimized conditions. The demonstrated synthesis technique for\narrayed WS<sub>2</sub>-NTs will play a central role in the fabrication\nof devices using transition-metal dichalcogenide nanotubes.