Elastic Properties and Fracture Behaviors of Biaxially Deformed, Polymorphic MoTe₂

Abstract

Biaxial deformation of suspended membranes widely exists and is used in nanoindentation to probe elastic properties of structurally isotropic two-dimensional (2D) materials. However, the elastic properties and, in particular, the fracture behaviors of anisotropic 2D materials remain largely unclarified in the case of biaxial deformation. MoTe2 is a polymorphic 2D material with both isotropic (2H) and anisotropic (1T′ and T d) phases and, therefore, an ideal system of single-stoichiometric materials with which to study these critical issues. Here, we report the elastic properties and fracture behaviors of biaxially deformed, polymorphic MoTe2 by combining temperature-variant nanoindentation and first-principles calculations. It is found that due to similar atomic bonding, the effective moduli of the three phases deviate by less than 15%. However, the breaking strengths of distorted 1T′ and T d phases are only half the value of 2H phase due to their uneven distribution of bonding strengths. Fractures of both isotropic 2H and anisotropic 1T′ phases obey the theorem of minimum energy, forming triangular and linear fracture patterns, respectively, along the orientations parallel to Mo–Mo zigzag chains. Our findings not only provide a reference database for the elastic behaviors of versatile MoTe2 phases but also illuminate a general strategy for the mechanical investigation of any isotropic and anisotropic 2D materials.

Thermomechanical Nanocutting of 2D Materials

“…Our direct nanofabrication technique is not limited to monolayer MoTe 2 but can be also used to cut other 2D materials, certain multilayers and, most interestingly, also heterostructures. To break the 2D layer apart, the indenting tip has to induce sufficient deformation to reach the failure strain of about 10% for MoTe 2 , [ 25 ] 10% for MoS 2 , [ 26 ] 2.6% for MoSe 2 , [ 27 ] and 12% for graphene, [ 28,29 ] respectively, as confirmed by our experiments. For instance, a 1L MoS 2 concentric nanostructure and a 1L MoSe 2 nanoribbon array are also readily fabricated (Section S3, Supporting Information).…”

“…The indentation depth of these structures corresponds to straining the 2D layer twice as high as the calculated breaking strength. [ 25 ] Although it is difficult to experimentally determine the strain at which the 2D material breaks, these results clearly show that a cut has been achieved. Nanocutting of continuous lines in 1L MoTe 2 is also successfully conducted in a labyrinth pattern (Figure 1g) with a linewidth of 50 nm as shown in Figure 1h–j.…”

“…These 2D materials have breaking strengths ranging from 3 to 42 N m −1 . [ 25–29 ] Depending on this value, the cutting can be performed, or not, at a given writing temperature and indentation force. We first designed a test pattern consisting of nanosquare arrays and a labyrinth pattern in a 1L MoTe 2 flake (Figure 1c).…”

Two‐dimensional materials: From mechanical properties to flexible mechanical sensors

“…The above two strategies were widely used to investigate the elastic property, intrinsic strength, and bending rigidity of graphene, MoS 2 , boron nitride (BN), MoTe 2 , and black phosphorus (BP) . Despite impressive progress in the mechanical properties study of 2D materials, there are still challenges in the accurate characterization of mechanical properties for partial 2D materials like MoTe 2 . It is also challenging to acquire freely suspended chemical vapor deposition (CVD)‐grown MoTe 2 and WTe 2 because they are unstable and decompose within several minutes in the air.…”

Mechanical and Thermal Properties of Graphene over Composite Materials: A Technical Review

“…Graphene materials have stable mechanical properties that have future application prospects in the nanoelectromechanical field. The fundamental exact starter examination of the versatile properties and quality of reduced graphene was finished by Lee et al [55] It was discovered that the graphene exhibits both fragile split and non-arranged versatile leads. Min et al [56] assessed the shear quality, shear modulus, and split strain of graphene as a part of temperature and chirality through atomic reenactments and announced a break worry of 97.54 GPa and shear nature of 60 GPa when the graphene sheet is exceptionally level.…”