Argon Plasma Induced Phase Transition in Monolayer MoS₂

Abstract

In this work, we report a facile, clean, controllable and scalable phase engineering technique for monolayer MoS. We found that weak Ar-plasma bombardment can locally induce 2H→1T phase transition in monolayer MoS to form mosaic structures. These 2H→1T phase transitions are stabilized by point defects (single S-vacancies) and the sizes of induced 1T domains are typically a few nanometers, as revealed by scanning tunneling microscopy measurements. On the basis of a selected-area phase patterning process, we fabricated MoS FETs inducing 1T phase transition within the metal contact areas, which exhibit substantially improved device performances. Our results open up a new route for phase engineering in monolayer MoS and other transition metal dichalcogenide (TMD) materials.

2D superconductivity and vortex dynamics in 1T-MoS2

“…1T-MoS2, metallic in nature with high carrier concentration, qualifies the resistance requirement to exhibit 2D superconductivity. 1T phase is generally prepared by structural modification of the 2H phase either by chemical intercalation 45 or by physical means using highenergy electrons or plasma treatment [46][47][48] . Stability of the 1T phase is a highly debated topic.…”

Surface Engineering of MoS2 via Laser‐Induced Exfoliation in Protic Solvents

“…The most stable hexagonal 2H MoS 2 possesses the semiconducting properties and a limited number of active sites confined on the edges, whereas the octahedral 1T MoS 2 exhibits the metallic properties and superior catalytic performances owing to the preferable charge transport and abundant active sites on basal planes . Hence, much effort has been devoted to the development of strategies to prepare 1T phase MoS 2 , either by direct synthesis or conversion from 2H phase MoS 2 , including alkali metal intercalation, mechanical strain, electron‐beam irradiation, plasma bombardment, supercritical CO 2 ‐induced, and hydrothermal synthesis . On the other hand, S vacancies on the basal plane of 2H MoS 2 provide the active sites for efficiently catalyzing HER, in addition to the edge sites.…”

“…These protons react with bulk MoS 2 and extract S atoms to produce H 2 S gas during the laser exfoliation process, creating S vacant sites on the basal plane of MoS 2 . It was suggested that such creation of S vacancies can facilitate the gliding of S atoms to form 1T phase MoS 2 . However, no 2H‐to‐1T phase transition was observed from MoS 2 in the presence of only protons .…”

A machine perspective of atomic defects in scanning transmission electron microscopy

“…While other metal dopants of group VIIB‐to‐IB exhibit no magnetism, which is attributed to the symmetry collapse from C 3v to C 1 as suggested by the observation of a Jahn‐Teller effect. The defect topology can be further modified by various irradiation methods . A point defect cluster with 3‐fold symmetry, referred to as a trefoil defect, was observed at elevated temperature in monolayer WSe 2 under electron irradiation .…”

“…The defect topology can be further modified by various irradiation methods. [55][56][57][58][59][60][61][62][63][64][65] A point defect cluster with 3-fold symmetry, referred to as a trefoil defect, was observed at elevated temperature in monolayer WSe 2 under electron irradiation. 58 Figure 2C,D shows the ADF-STEM images of connected Se vacancies and T1 defects before and after the transformation, with the atomic models displayed in the lower panels.…”