Strain-Induced Performance Enhancement of a Monolayer Photodetector via Patterned Substrate Engineering

Two-dimensional (2D) materials exhibit tremendous potential for applications in next-generation photodetectors. Currently, approaches aiming at enhancing the device's performance are limited, mainly relying on complex hybrid systems such as heterostructures and sensitization. Here, we propose a new strategy by constructing patterned nanostructures compatible with the conventional silicon substrate. Using CVD-grown monolayer MoS₂ on the periodical nanocone arrays, we demonstrate a high-performance MoS₂ photodetector via manipulating strain distribution engineered by the substrate at the nanoscale. Compared to the pristine MoS₂ counterpart, the strained MoS₂ photodetector exhibits a much enhanced performance, including a high signal-to-noise ratio over 10⁵ and large responsivity of 3.2 × 10⁴ A W^-1. The physical mechanism responsible for the enhancement is discussed by combining Kelvin probe force microscopy with theoretical simulation. The enhanced performances can be attributed to the improved light absorption, the fast separation of photo-excited carriers, and the suppression of dark currents induced by the designed periodical nanocone arrays. This work depicts an alternative method to achieve high-performance optoelectronic devices based on 2D materials integrated with semiconductor circuits.