Silver-ion-passivated black phosphorus photodetectors to improve the response time

Abstract

We present a remarkable improvement in the photoresponse time of few-layer black phosphorus (BP) following treatment with silver nitrate solution, with the rise time being reduced from 1.71 s to 50 ms and the fall time being reduced from 3.25 s to 80 ms. X-ray photoelectron spectroscopy (XPS) was utilized to analyze the surface of the treated BP flakes, and the role of Ag⁺ in diminishing the surface activity of BP devices was evaluated. Moreover, the adsorption of Ag⁺ was observed to effectively hinder the oxidation of the BP surface, resulting in a decrease of the hysteresis from 85.6 V to 29 V. By analyzing the correlation coefficients of photocurrent and laser power, we suggest that the improved performance of the photodetector is caused by the presence of BP(Ag⁺) on the surface, which significantly decreases the concentration of defects in BP and thus the concentration of trap states.