Improving photodetection response time of ReS2 devices through double-sided oxidation

Response time is a crucial factor limiting the performance of two-dimensional material-based photodetectors. The underlying mechanisms of response have recently garnered significant attention in the ongoing research. Supported ReS2 on substrates has been found to be predominantly governed by the photofloating gate effect, known to be slower compared to photoelectric effects. In this study, we present findings demonstrating suspended ReS2 devices. Removing the substrate results in a substantial enhancement in optical response by an order of magnitude compared to substrate-supported devices. Deep trap states induced by inherent defects are identified as the primary contributors to prolonged response times. Engineering these ReS2 trap states through defect manipulation can significantly improve response times. Here, we effectively modulate the response speed of ReS2 through gentle oxygen plasma treatments. The response speed of ReS2 is improved by two orders of magnitude. Under the optimal processing conditions of 50 W, 30 Pa, and 10 s, we observed rising and falling response times of 45 and 106 ms, respectively, under illumination at a wavelength of 637 nm. Additionally, we demonstrate that the input–output characteristic of photocurrent provides valuable insights into the underlying opto-physical processes responsible for generating photocurrent.