Recovery of the Pristine Surface of Black Phosphorus by Water Rinsing and Its Device Application

Black phosphorus (BP) has attracted significant attention due to its excellent optical and electrical properties. However, the rapid degradation of BP under ambient air limits further research on its properties and implementation in various fields. This degrading behavior lowers the performance of BP-based devices and can even result in a complete failure when exposed to air for an extended period of time. In our research, the degraded surface with "bubbles" was recovered to its pristine state by rinsing with deionized water and following with post-treatments. The formation of bubbles and their optical, morphological, and electrical effects were systematically investigated by fabricating BP field-effect transistors (FETs) in conjunction with micro-Raman spectroscopy and atomic force microscopy. Water rinsing of the degraded BP flakes also allowed us to thin BP flakes down because phosphorus atoms are consumed while forming bubbles. Therefore, recovery of the pristine surface not only results in a smoother and thinner morphology but also improves device performances. After the rinsing process, field-effect mobility of the BP FET was maintained, whereas a significant enhancement in the switching behaviors was achieved in conclusion. The capability of reversing the inevitable degradation that occurs once exposed to ambient conditions can open up new opportunities for further applications of BP that was limited due to its instability.