Improved Metal-Semiconductor Interface in Monolayer (1L)-MoS2 via Thermally-Driven Ag Filaments as Atomic Scale Edge Contacts Triggered by Selective Annealing Process Using Long Wavelength (1064 nm) Pulsed Laser.

Abstract

Here, we explore the effectiveness of a pulsed laser annealing (PLA) process to trigger atomic scale edge contacts by Ag filaments in reducing the contact resistance of a MoS₂ field-effect transistor (FET). Employing a long wavelength (1064 nm) pulsed laser, we anneal monolayer (1L)-MoS₂ FETs with various metal electrodes, including Ag/Au, Ni/Au, and Cr/Au. A remarkable enhancement in FET performance could be achieved after the PLA treatment. Specifically, Ag/Au-contacted 1L-MoS₂ FETs after the PLA treatment exhibit a peak field-effect mobility increase from 60 to 135 cm² V^-1 s^-1 and an on-current improvement from 40.5 to 96.1 μA at a Vd of 1 V, accompanied by a significant decrease in contact resistance to 0.29 kΩ μm. PLA-treated 1L-MoS₂ FETs showed a high on/off ratio of 10⁷. TEM analysis provided insight into the mechanism of reduced contact resistance, revealing the thermally driven diffusion of Ag atoms into the 1L-MoS₂ as Ag filaments to lateral contact with the edge of the 1L-MoS₂, namely atomic scale edge contacts, as a key contributing factor. Furthermore, our investigation extends to the larger scale CVD-grown 1L-MoS₂ films, where the PLA treatment demonstrates notable improvements in mobility, on-current, and on-off ratio.