Nanoindentation, [2,[6][7][8] the analysis of the dynamics of nanomechanical resonators, [9] and the microscopic adaptation of tensile tests setups [10] or Brillouin scattering [11] have been developed to characterize the fundamental mechanical properties of 2D materials such as their Young's modulus. [12,13] Although powerful, these techniques require dedicated setups and rather complex data acquisition and/or analysis. Alternative to these methods, Stafford et al. [14] introduced the buckling metrology method, a simple and elegant way to measure the Young's modulus of thin polymeric films by studying the buckling instability, which arises when the film is deposited onto a compliant substrate, and it is subjected to uniaxial compression. [15] Under these conditions, the trade-off between the adhesion forces between film and substrate and the bending rigidity of the film leads to a rippling of the thin film with a characteristic wavelength that only depends on the elastic properties of the film and the substrate. This elegant method to characterize the mechanical properties of thin films has been extensively used to study coatings [14] and organic semiconducting materials. [16] However, it has been scarcely employed to study 2D materials, [17][18][19][20] and it seems that is has been mostly overlooked by the 2D materials community.Here, we apply the buckling-based metrology method to determine the Young's modulus of transition metal dichalcogenide (TMDC) flakes with thickness ranging from 2 layers up to 10 layers. We use optical microscopy to determine both the number of layers and the rippling wavelength, which is therefore very fast and simple to implement. We critically compare the results obtained with this method and demonstrate that despite its simplicity it provides results in good agreement with other techniques to study the mechanical properties of 2D materials. We believe that the buckling-based metrology method provides a fast route to determine the Young's modulus of 2D materials, being an excellent alternative to other existing nanomechanical test methods that are more technically demanding.The samples are fabricated by mechanical exfoliation of bulk layered TMDC crystals with adhesive tape (see Experimental Section for details). The exfoliated material is then transferred onto a compliant elastomeric substrate (Gel-Film, a commercially available polydimethylsiloxane, PDMS, film manufactured by Gel-Pak) which is subjected to a uniaxial stress of ≈20%. Right after the transfer, the stress on the elastomeric Measuring the mechanical properties of 2D materials is a formidable task. While regular electrical and optical probing techniques are suitable even for atomically thin materials, conventional mechanical tests cannot be directly applied. Therefore, new mechanical testing techniques need to be developed. Up to now, the most widespread approaches require micro-fabrication to create freely suspended membranes, rendering their implementation complex and costly. Here, a simple yet powerful technique is ...
Probing the mechanical properties of two‐dimensional materials represents a challenging task due to their reduced dimensions. In article number https://doi.org/10.1002/adma.201807150, Andres Castellanos‐Gomez and co‐workers demonstrate the feasibility to determine the Young's modulus of atomically thin crystals through the buckling metrology method: uniaxial compression of two‐dimensional materials leads to formation of ripples, whose wavelength is intrinsically related to their mechanical properties.
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