Synthesis of Arrayed Tungsten Disulfide Nanotubes.

Tungsten disulfide nanotubes (WS-NTs), with their cylindrical structure composed of rolled WS sheets, have attracted much interest because of their unique physical properties reflecting quasi-one-dimensional chiral structures. They exhibit a semiconducting electronic structure regardless of their chirality, and various semiconducting and optoelectronic device applications have been demonstrated. The development of techniques to fabricate arrayed WS-NTs is crucial to realizing the highest device performance. Since the discovery of WS-NTs, various synthesis techniques have been reported; however, horizontally arrayed WS-NTs have never been successfully synthesized. Here, we demonstrate a simple technique to synthesize arrayed WS-NTs. Through precise temperature and gas control, WO nanowires are grown along the [1̅101] direction on an r-plane sapphire substrate, and the nanowires are converted into nanotubes via sulfurization under optimized conditions. The demonstrated synthesis technique for arrayed WS-NTs will play a central role in the fabrication of devices using transition-metal dichalcogenide nanotubes.