Ultra-fast and high flexibility near-infrared photodetectors based on Bi₂Se₃ nanobelts grown via catalyst-free van der Waals epitaxy

van der Waals epitaxy (vdWe) method has recently attracted considerable interest due to its extensive application in the growth of layered structure materials. However, the growth process of vdWe is not completely understood. Here, we report the controlled growth process of Bi₂Se₃ nanobelts and study their photoresponse behaviour. The average length of nanobelts increases from 7 μm to 17 μm by adjusting the temperature of Bi₂Se₃ powder from 520 °C to 530 °C, however the average length becomes saturated with further increasing the source material temperature over 530 °C. Such a change can be attributed to the competition between the process of Bi₂Se₃ molecule diffusion and the process of crystal formation-related chemical reaction, leading to a symmetrically studying for the growth process of catalyst-free vdWe growth of Bi₂Se₃ nanobelts. The photodetectors based on these Bi₂Se₃ nanobelts show excellent device performance in the near-infrared light range, including an ultra-fast photoresponse (t_rsing ≈ 37 ms, t_decay ≈ 62 ms), a high responsivity of 10.1 mA/W and a high detectivity of 4.63 × 10⁸ Jones. This high device performance could be related to the excellent carrier transport properties as Bi₂Se₃ nanobelt photodetectors also demonstrate a great potential for fabricating flexible and wearable electronics by still showing stable photoresponse after bending the device for 200 times.