Atomic Structure of Intrinsic and Electron-Irradiation-Induced Defects in MoTe₂

Abstract

Studying the atomic structure of intrinsic defects in two-dimensional transition-metal dichalcogenides is difficult since they damage quickly under the intense electron irradiation in transmission electron microscopy (TEM). However, this can also lead to insights into the creation of defects and their atom-scale dynamics. We first show that MoTe2 monolayers without protection indeed quickly degrade during scanning TEM (STEM) imaging, and discuss the observed atomic-level dynamics, including a transformation from the 1H phase into 1T′, 3-fold rotationally symmetric defects, and the migration of line defects between two 1H grains with a 60° misorientation. We then analyze the atomic structure of MoTe2 encapsulated between two graphene sheets to mitigate damage, finding the as-prepared material to contain an unexpectedly large concentration of defects. These include similar point defects (or quantum dots, QDs) as those created in the nonencapsulated material and two different types of line defects (or quantum wires, QWs) that can be transformed from one to the other under electron irradiation. Our density functional theory simulations indicate that the QDs and QWs embedded in MoTe2 introduce new midgap states into the semiconducting material and may thus be used to control its electronic and optical properties. Finally, the edge of the encapsulated material appears amorphous, possibly due to the pressure caused by the encapsulation.

Can Reconstructed Se‐Deficient Line Defects in Monolayer VSe2 Induce Magnetism?

“…The decomposition of chalcogenides from TMD crystals to create individual chalcogenide vacancies or line patterns is a low‐energy process, and has been reported to be induced via annealing, electron beam or laser irradiation. [ 23,30–32 ] In contrast, the structural reconstruction to form pure 8‐member‐ring arrays proposed here has not been observed yet, to the best of our knowledge. One possible reason is that such reconstruction process involved a lateral sliding requires higher energy and thus only occurs upon annealing at elevated temperatures.…”

2D Material Science: Defect Engineering by Particle Irradiation

“…For transition metal dichalcogenides (TMDs), chalcogen vacancies are the most observed defects, often arranging into line defects [ 68 ] (see Figure 5 b). A commonly observed structural change in TMDs is a local phase transition [ 69 , 70 ], typically between the 1H and 1T phases (see Figure 5 c).…”

Revisiting the Role of Active Sites for Hydrogen Evolution Reaction through Precise Defect Adjusting

“…However, the chemical vapor deposition (CVD) of MoTe 2 with well morphological control ability, which is beneficial to research on the mechanism, is still not mature . On the other hand, MoTe 2 is not as stable as MoS 2 , having a strong tendency toward oxidation in the air9a and being quickly damaged under high‐energy irradiation . As a consequence, it is difficult for MoTe 2 to bear with the common defects of the engineering methods applied in the study of MoS 2 , such as O 2 plasma etching, Ar plasma etching, and other etching methods, leading to the lack of relevant research works of MoTe 2 .…”