Engineering the Crack Structure and Fracture Behavior in Monolayer MoS₂ By Selective Creation of Point Defects

Abstract

Monolayer transition‐metal dichalcogenides, e.g., MoS 2 , typically have high intrinsic strength and Young's modulus, but low fracture toughness. Under high stress, brittle fracture occurs followed by cleavage along a preferential lattice direction, leading to catastrophic failure. Defects have been reported to modulate the fracture behavior, but pertinent atomic mechanism still remains elusive. Here, sulfur (S) and MoS n point defects are selectively created in monolayer MoS 2 using helium‐ and gallium‐ion‐beam lithography, both of which reduce the stiffness of the monolayer, but enhance its fracture toughness. By monitoring the atomic structure of the cracks before and after the loading fracture, distinct atomic structures of the cracks and fracture behaviors are found in the two types of defect‐containing monolayer MoS 2 . Combined with molecular dynamics simulations, the key role of individual S and MoS n point defects is identified in the fracture process and the origin of the enhanced fracture toughness is elucidated. It is a synergistic effect of defect‐induced deflection and bifurcation of cracks that enhance the energy release rate, and the formation of widen crack tip when fusing with point defects that prevents the crack propagation. The findings of this study provide insights into defect engineering and flexible device applications of monolayer MoS 2 .

Modulation of Schottky Barrier Height by Nitrogen Doping and Its Influence on Responsivity of Monolayer MoS2 Photodetector

“…[1,2] Moreover, the direct bandgap nature present in monolayer MoS 2 is being exploited in many flexible and optoelectronic applications. [3,4] MoS 2 is known to have intrinsic n-type behavior, and there are previous reports suggesting the origin is sulfur vacancies. [5][6][7][8][9][10] The work function, which by definition is the energy required to free electrons from Fermi level, is an important parameter in deciding the performance of any electronic or optoelectronic device.…”

Deciphering Vacancy Defect Evolution of 2D MoS2 for Reliable Transistors

“…Figure a shows the main scenarios where active oxidation substances are inevitably introduced during the processing and in the servicing of MoS 2 devices, such as O 2 , H 2 O, −OH, etc. in wet transfer, patterned etching, insulating layer deposition, etc. , These active substances, especially O 2 , tend to initiate the evolution of defects. − Figure S1a shows the Gibbs free energy (Δ G ) of O 2 initiating S, V S , and V S2 in MoS 2 to produce V S , V S + V S , and V S2 + V S , respectively. The insets show the optimized geometries of O 2 initiating the evolution of different defects and the other two cases are shown in Figure S1b–c.…”

“…The formation of V MoxSy and nanopores is the manifestation of the stress release of the structure system. 16,33,34 When approaching the edge zone, in addition to the main vacancies, more and larger nanopores with the reconstructed Mo-Klein edge and 1T′ phase-transition edge can be seen owing to the structural collapse stress during the expansion of the nanopores (Figure 3f #5′). 35 These nanopores have trends of interconnection (Figure S10b #5′).…”

4D‐STEM Nanoscale Strain Analysis in van der Waals Materials: Advancing beyond Planar Configurations

“…Consistently, the magnitude of strain we observed perpendicular to the direction of the crack in the MoS 2 layer and the rotation across the entire nanostructure align with previously reported behaviors in MoS 2 monolayers, which have been attributed to the emergence of crack structures due to point defects. [58,59] Furthermore, in the xx direction, distinct regions displaying tensile strain, approximately ε xx ≃ 2% ð Þ , are evident. These strained regions can be predominantly linked to the vicinity of point defects and holes present in the MoS 2 layer, a visualization of which is provided in Figure 4a.…”