Threshold voltage modulation in monolayer MoS2 field-effect transistors via selective gallium ion beam irradiation

Electronic regulation of two-dimensional (2D) transition metal dichalcogenides (TMDCs) is a crucial step towards next-generation optoelectronics and electronics. Here, we demonstrate controllable and selective-area defect engineering in 2D molybdenum disulfide (MoS2) using a focused ion beam with a low-energy gallium ion (Ga+) source. We find that the surface defects of MoS2 can be tuned by the precise control of ion energy and dose. Furthermore, the field-effect transistors based on the monolayer MoS2 show a significant threshold voltage modulation over 70 V after Ga+ irradiation. First-principles calculations reveal that the Ga impurities in the monolayer MoS2 introduce a defect state near the Fermi level, leading to a shallow acceptor level of 0.25 eV above the valence band maximum. This defect engineering strategy enables direct writing of complex pattern at the atomic length scale in a controlled and facile manner, tailoring the electronic properties of 2D TMDCs for novel devices.

Automated summary

The precise control of ion energy and dose allows for tuning surface defects of MoS2, with significant threshold voltage modulation observed in field-effect transistors based on monolayer MoS2 after Ga+ irradiation. First-principles calculations reveal that Ga impurities in monolayer MoS2 introduce defect states near the Fermi level, leading to a shallow acceptor level of 0.25 eV above the valence band maximum.