Femtosecond Laser Irradiation-Mediated MoS₂–Metal Contact Engineering for High-Performance Field-Effect Transistors and Photodetectors

Abstract

2D materials exhibit intriguing electrical and optical properties, making them promising candidates for next-generation nanoelectronic devices. However, the high contact resistance of 2D materials to electrode material often limits the ultimate performance and potential of 2D materials and devices. In this work, we demonstrate a localized femtosecond (fs) laser irradiation process to substantially minimize the resistance of MoS2–metal contacts. A reduction of the contact resistance exceeding three orders of magnitude is achieved for mechanically exfoliated MoS2, which remarkably improves the overall FET performance. The underlying mechanisms of resistance reduction are the removal of organic contamination induced by the transfer process, as well as the lowering of Schottky barrier resistance (RSB) attributed to interface Fermi level pinning (FLP) by Au diffusion, and the lowering of interlayer resistance (Rint) due to interlayer coupling enhancement by Au intercalation under fs laser irradiation. By taking advantage of the improved MoS2–metal contact behavior, a high-performance MoS2 photodetector was developed with a photoresponsivity of 68.8 A W–1 at quite a low Vds of 0.5 V, which is ∼80 times higher than the pristine multilayer photodetector. This contamination-free, site-specific, and universal photonic fabrication technique provides an effective tool for the integration of complex 2D devices, and the mechanism of MoS2–metal interface modification reveals a new pathway to engineer the 2D material–metal interface.