Ultrafast and hypersensitized detection based on van der Waals connection in two-dimensional WS2/Si structure

Abstract

WS2, as a typical transition-metal dichalcogenides (TMDs) with strong light–matter interaction, exhibits great potential for highly-responsive photoelectric detectors. In this work, a series of WS2 nano-films with different thicknesses are successfully prepared on Si substrate by atomic layer deposition (ALD) and present a high-performance lateral photovoltaic effect (LPE). It shows high position sensitivity (up to 232 mV mm−1) and ultrafast response speed of 4.1 μs with little signal degeneration because of the strong light absorptivity and carrier mobility in the layered structure connected by van der Waals force. In addition, we find the absorption wavelength of lateral photovoltage (LPV) has changed significantly when WS2 thickness decreases to several layers. We attribute this phenomenon to the increasing indirect band-gap of WS2. It establishes an association between materials bandgap and LPV, which may suggest a potential approach for the characterization of theof bandgap and thickness of 2D materials.