What is it about?
Strain measures how much a given deformation differs locally from its original shape. Strain engineering is typically used in the semiconductor industry to build faster transistors. Two-dimensional (2D) materials are a new type of material that could be as thin as 1 nm. 2D materials have unique properties that could sustain strain up to 25%. However, reversible applying strain on 2D materials is challenging due to the lack of bonding between the substrate and the 2D materials. Using an oven treated as low as the temperature to boiling the water, you can make the straining of 2D materials on polymer substrate more robust and reproducible. After this treatment, the morphology of 2D materials on polymer substrate changed dramatically, and the materials could survive in water for days to weeks. We anticipate the facile methodology and understanding of the straining could boost the field of 2D materials and devices.
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Photo by Anna Samoylova on Unsplash
Why is it important?
Improving strain engineering experiments in 2D materials could lead to a new generation of strain tunable devices (e.g. emitters, photodetectors). The approach used in this work to suppress the slippage and improve strain transfer will be helpful for many researchers working on strain engineering of 2D materials.
Perspectives
Our methodology demonstrates an efficient and fast method to enhance the straining of 2D materials by a low-pressure thermal annealing process.
Yong Xie
Xidian University
Read the Original
This page is a summary of: Straining of atomically thin WSe2 crystals: Suppressing slippage by thermal annealing, Journal of Applied Physics, August 2022, American Institute of Physics,
DOI: 10.1063/5.0096190.
You can read the full text:
Resources
An Automated System for Strain Engineering and Straintronics of 2D Materials
This work presents an automated three-point bending apparatus that can be used to study strain engineering and straintronics in 2D materials. This work benchmarks the system by reporting reproducible strain-tuned micro-reflectance, Raman, and photoluminescence spectra for monolayer molybdenum disulfide (MoS2). These results are in good agreement with reported literature using conventional bending apparatus. This work further utilizes the system to automate strain investigations of straintronic devices by measuring the piezoresistive effect and the strain effect on photoresponse in an MoS2 electrical device. The details of the construction of the straightforward system are given and it is anticipated that it can be easily implemented for the study of strain engineering and straintronics in a wide variety of 2D material systems.
Stretching ReS2 along different crystal directions: Anisotropic tuning of the vibrational and optical responses
Rhenium disulfide (ReS2) is a semiconducting two-dimensional material with marked in-plane structural anisotropy. This lattice anisotropy is the stem of many quasi-1D properties observed in this material. In this work, we focus on strain engineering of optical and vibrational properties through mechanical deformations of the lattice. In particular, the exciton energy can be shifted by applying uniaxial strain, and the gauge factor is six times more pronounced when the strain is applied along the b-axis than in perpendicular to the b-axis of the ReS2 lattice. Moreover, we also observed how the two most prominent Raman modes can be shifted by uniaxial strain, and the shift strongly depends on the alignment between the uniaxial strain direction and the a- and b-axes of the ReS2 lattice.
Straining and Tuning Atomic Layer Nanoelectromechanical Resonators via Comb‐Drive MEMS Actuators
Broad frequency tuning is an essential attribute desired in resonant nano/microelectromechanical systems (NEMS/MEMS) and their many applications. Endowed with ultrahigh intrinsic strain limits, combined with other unconventional properties, atomically thin 2D crystalline materials are excellent candidates for building highly tunable resonant NEMS. Here a heterogeneous integration approach is demonstrated to enable on-chip, continuous, and broad frequency tuning in 2D NEMS resonators by directly controlling strain via voltage-controlled silicon-on-insulator (SOI) comb-drive MEMS actuators. By varying the comb-drive actuation voltage, resonance frequency of the 2D NEMS can be tuned as large as 75% continuously with precise control. The comb-drive actuation-enabled direct straining and tuning also yield quality (Q) factor boost up to twofold. It is validated that this technique is readily applicable to straining and tuning representative 2D NEMS in various leading materials: graphene, molybdenum disulfide (MoS2), and hexagonal boron nitride (h-BN). This study demonstrates that additively integrating 2D resonators atop mainstream SOI MEMS enables a versatile platform, and opens new possibilities for voltage control and broad tuning of 2D NEMS on chip.
Unusual Deformation and Fracture in Gallium Telluride Multilayers
The deformation and fracture mechanism of two-dimensional (2D) materials are still unclear and not thoroughly investigated. Given this, mechanical properties and mechanisms are explored on example of gallium telluride (GaTe), a promising 2D semiconductor with an ultrahigh photoresponsivity and a high flexibility. Hereby, the mechanical properties of both substrate-supported and suspended GaTe multilayers were investigated through Berkovich-tip nanoindentation instead of the commonly used AFM-based nanoindentation method. An unusual concurrence of multiple pop-in and load-drop events in loading curve was observed. Theoretical calculations unveiled this concurrence originating from the interlayer-sliding mediated layers-by-layers fracture mechanism in GaTe multilayers. The van der Waals force dominated interlayer interactions between GaTe and substrates was revealed much stronger than that between GaTe interlayers, resulting in the easy sliding and fracture of multilayers within GaTe. This work introduces new insights into the deformation and fracture of GaTe and other 2D materials in flexible electronics applications.
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