Highly Sensitive Phototransistors Based on Partially Suspended Monolayer WS₂

Abstract

Two-dimensional (2D) materials have attracted tremendous interests because of various advantages, such as high carrier mobility, favorable band gap, strong light-matter interaction, and flat dangling-bond-free surface. However, the photodetection performance of the pristine monolayer 2D materials is not competitive with that of their bulk counterpart due to the atomic thickness. Here, we demonstrated the direct growth of monolayer WS 2 on the Si 3 N 4 substrate by chemical vapor deposition. The porous morphology is formed at the surface of the Si 3 N 4 substrate during the growth process, and therefore, the as-grown WS 2 is partially suspended on porous Si 3 N 4 . The phototransistor based on as-grown monolayer WS 2 exhibits a high responsivity of 1.58 × 10 5 A/W and a fast response speed of 40 ms. Because of light resonant scattering of the porous Si 3 N 4 substrate, the absorption coefficient of monolayer WS 2 is enhanced from finite element analysis. In addition, biaxial tensile strain distribution in the partially suspended WS 2 induces a built-in in-plane electric field and less carrier mass from first-principles calculations. Therefore, we attributed the high performance of the phototransistor to the hybrid structure of partially suspended monolayer WS 2 on the porous substrate. Our present work paves a way to achieve high-performance monolayer photodetector from substrate morphology engineering.

Self-Powered Programmable van der Waals Photodetectors with Nonvolatile Semifloating Gate

“…It is worth noting that these performance parameters may be potentially underestimated due to the overestimated active area of the SFG-PD. Additionally, R and D * align closely with the calculated absorbance of 6.3 nm MoTe 2 (Figure S8) using the Lambert–Beer law and the reported experimental data of trilayer MoTe 2 , which can potentially be further enhanced through optical or plasmonic resonances. ,, …”

“…This surge in attention is particularly evident with the advancement of programmable , and neuromorphic − optoelectronics. The photovoltaic response is characterized by attributes such as low-power consumption, rapid response, and low dark current. − This behavior is commonly attributed to the built-in electric field within various junctions, including p + -p, p-n, n + -n, and Schottky junctions, which are typically fabricated through processes such as chemical doping, , materials stacking, , epitaxial growth, , local split gating, − strain engineering, , or asymmetric contacting. − Distinguished by the volatile or nonvolatile nature of these junctions, two strategies involving continuous and pulsed voltage application are typically employed to tune the photovoltaic photoresponse, enabling transitions from negative to positive responses. For example, in certain narrow-bandgap 2D semiconductor-based heterojunctions (e.g., BP/MoTe 2 , PdSe 2 /MoTe 2 , AsP/MoS 2 ) and the configuration of ambipolar 2D semiconductor-based homojunctions (e.g., BP, WSe 2 , MoTe 2 ), the band alignment can be effectively modulated through continuous global gating and split gating, respectively, resulting in gate-tunable photoresponse.…”

MoS2 / WS2 Nanosheets and Quantum Dots for Sensing Hemin and Fabrication of Self-Powered Photodetectors

“…24 Furthermore, their tunable band gap is complemented by strong photoluminescence and high exciton binding energy, positioning them as promising candidates for a wide range of optoelectronic devices such as solar cells, 25 light-emitting diodes, 26 photodetectors, 27 and phototransistors. 28 However, the conventional routes for preparing TMDC are not straightforward. For example, chemical vapor deposition is a very sophisticated setup and employs toxic precursors leading to safety concerns and operational complexities.…”

“…TMDC, especially MoS 2 and WS 2 , are extensively used in different applications ranging from nanoelectronics and nanophotonics to sensing and as a catalyst . Furthermore, their tunable band gap is complemented by strong photoluminescence and high exciton binding energy, positioning them as promising candidates for a wide range of optoelectronic devices such as solar cells, light-emitting diodes, photodetectors, and phototransistors . However, the conventional routes for preparing TMDC are not straightforward.…”