Fabrication of Single-Crystal Violet Phosphorus Flakes For Ultrasensitive Photodetection

Violet phosphorus (VP) has attracted a lot of attention for its unique physicochemical properties and emerging potential in photoelectronic applications. Although VP has a van der Waals (vdW) structure similar to that of other 2D semiconductors, direct synthesis of VP on a substrate is still challenging. Moreover, optoelectronic devices composed of transfer-free VP flakes have not been demonstrated. Herein, a bismuth-assisted vapor phase transport technique is designed to grow uniform single-crystal VP flakes on the SiO₂/Si substrate directly. The size of the crystalline VP flakes is an order of magnitude larger than that of previous liquid-exfoliated samples. The photodetector fabricated with the VP flakes shows a high responsivity of 12.5 A W⁻¹ and response/recovery time of 3.82/3.03 ms upon exposure to 532 nm light. Furthermore, the photodetector shows a small dark current (<1 pA) that is beneficial to high-sensitivity photodetection. As a result, the detectivity is 1.38 × 10¹³ Jones that is comparable with that of the vdW p–n heterojunction detector. The results reveal the great potential of VP in optoelectronic devices as well as the CVT technique for the growth of single-crystal semiconductor thin films. © 2024 Wiley-VCH GmbH.