Mechanical Properties and Strain Transfer Behavior of Molybdenum Ditelluride (MoTe2) Thin Films

Abstract

Transition metal dichalcogenides (TMDs) offer superior properties over conventional materials in many areas such as in electronic devices. In recent years, TMDs have been shown to display a phase switching mechanism under the application of external mechanical strain, making them exciting candidates for phase change transistors. Molybdenum ditelluride (MoTe2) is one such material that has been engineered as a strain-based phase change transistor. In this work, we explore various aspects of the mechanical properties of this material by a suite of computational and experimental approaches. Firstly, we present parameterization of an interatomic potential for modeling monolayer as well as multilayered MoTe2 films. For generating the empirical potential parameter set, we fit results from Density Functional Theory calculations using a random search algorithm called particle swarm optimization. The potential closely predicts structural properties, elastic constants, and vibrational frequencies of MoTe2 indicating a reliable fit. Our simulated mechanical response matches earlier larger scale experimental nanoindentation results with excellent prediction of fracture points. Simulation of uniaxial tensile deformation by Molecular Dynamics shows the complete non-linear stress-strain response up to failure. Mechanical behavior, including failure properties, exhibits directional anisotropy due to the variation of bond alignments with crystal orientation. Furthermore, we show the deterioration of mechanical properties with increasing temperature. Finally, we present computational and experimental evidence of an extended c-axis strain transfer length in MoTe2 compared to TMDs with smaller chalcogen atoms.

An Atomistic Insight into Moiré Reconstruction in Twisted Bilayer Graphene beyond the Magic Angle

“…Molecular statics (MS) simulations were done using LAMMPS open source software. , The unstrained, DFT relaxed TBG moiré lattice was transformed into an orthogonal cell for performing MS simulations. The simulation box is considered with free surface boundary conditions in the direction of uniaxial strain, allowing us to account for the aperiodic crystal geometry (or moiré lattice mismatch) due to strain applied to one of the TBG layers.…”

2D Materials for Wearable Energy Harvesting

“…[175,176] Other TMDCs, including MoSe 2 and MoTe 2 , displayed comparable mechanical properties, such as a high Young's modulus and strength. [177][178][179][180] Due to their diverse chemical compositions and structural phases, TMDCs exhibit a broad spectrum of electrical properties, ranging from metallic to semiconductor to insulator, as well as unique topological electronics phases. [159,[181][182][183][184] Specifically, the electronic properties of TMDCs are strongly dependent on the filling of the transition metal ions' nonbonding d orbitals: metallic behavior occurs when the nonbonding d orbitals are partially filled, while semiconducting behavior occurs when all nonbonding d orbitals are occupied.…”

“…[ 175,176 ] Other TMDCs, including MoSe 2 and MoTe 2 , displayed comparable mechanical properties, such as a high Young's modulus and strength. [ 177–180 ]…”

Graphene and Beyond: Recent Advances in Two-Dimensional Materials Synthesis, Properties, and Devices

“…Similarly, recent results have shown that depositing stressed thin films onto 2D materials can induce strain transfer into the 2D material itself (Figure 14b). 208,214,215 This technique relies on the fact that thin films typically have some amount of process induced stress from deposition, and this stress can relax by transferring strain into the 2D material. This has been shown to be controllable in magnitude by varying film stress as well as controllable in type (uniaxiality vs biaxiality) and directionality through lithographic patterning.…”