Synthesis of Arrayed Tungsten Disulfide Nanotubes

Tungsten disulfide nanotubes (WS₂-NTs), with their cylindrical structure composed of rolled WS₂ 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 WS₂-NTs is crucial to realizing the highest device performance. Since the discovery of WS₂-NTs, various synthesis techniques have been reported; however, horizontally arrayed WS₂-NTs have never been successfully synthesized. Here, we demonstrate a simple technique to synthesize arrayed WS₂-NTs. Through precise temperature and gas control, W₁₈O₄₉ 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 WS₂-NTs will play a central role in the fabrication of devices using transition-metal dichalcogenide nanotubes.