Growth of few-layer WTe 2 by a salt-assisted double-tube chemical vapor deposition method with high infrared photosensitivity.

WTe 2 , as a member of Weyl semimetals, is a vital candidate for the development of broad-wavelength-range photodetectors. At present, the preparation of WTe 2 films mainly depends on the chemical vapor deposition (CVD) method. However, the chemical reactivity between W and Te is low, and the controllable synthesis of large-sized layered WTe 2 in a stoichiometric ratio is the main challenge for further research. Here, we propose a salt-assisted double-tube CVD method for the one-step preparation of high-quality and large-size WTe 2 crystals with a monolayer and few layers. The thickness and lateral dimension of WTe 2 crystals can be effectively tuned by the growth temperature and hydrogen concentration, and the dynamic growth mechanism is understood by the combination of surface reaction and mass transport. Furthermore, a high-performance photodetector based on WTe 2 is fabricated, which has high responsivity of 118 mA W -1 (1550 nm) and 408 mA W -1 (2700 nm) at room temperature, indicating its great potential for application in infrared optoelectronic devices. The results provide a reference for the preparation of 2D materials by CVD and lay the foundation for the fabrication of next-generation optoelectronic devices with a wide-wavelength-range response.