Nanoscale Adhesion and Material Transfer at 2D MoS2–MoS2 Interfaces Elucidated by In Situ Transmission Electron Microscopy and Atomistic Simulations

Low-dimensional materials, such as MoS2, hold promise for use in a host of emerging applications, including flexible, wearable sensors due to their unique electrical, thermal, optical, mechanical, and tribological properties. The implementation of such devices requires an understanding of adhesive p...

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Bibliographic Details
Published in:ACS applied materials & interfaces 2024-05, Vol.16 (23), p.30506-30520
Main Authors: Toom, Sathwik Reddy, Sato, Takaaki, Milne, Zachary, Bernal, Rodrigo A., Jeng, Yeau-Ren, Muratore, Christopher, Glavin, Nicholas R., Carpick, Robert W., Schall, J. David
Format: Article
Language:English
Subjects:
Surfaces, Interfaces, and Applications
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Summary:Low-dimensional materials, such as MoS2, hold promise for use in a host of emerging applications, including flexible, wearable sensors due to their unique electrical, thermal, optical, mechanical, and tribological properties. The implementation of such devices requires an understanding of adhesive phenomena at the interfaces between these materials. Here, we describe combined nanoscale in situ transmission electron microscopy (TEM)/atomic force microscopy (AFM) experiments and simulations measuring the work of adhesion (W adh) between self-mated contacts of ultrathin nominally amorphous and nanocrystalline MoS2 films deposited on Si scanning probe tips. A customized TEM/AFM nanoindenter permitted high-resolution imaging and force measurements in situ. The W adh values for nanocrystalline and nominally amorphous MoS2 were 604 ± 323 mJ/m2 and 932 ± 647 mJ/m2, respectively, significantly higher than previously reported values for mechanically exfoliated MoS2 single crystals. Closely matched molecular dynamics (MD) simulations show that these high values can be explained by bonding between the opposing surfaces at defects such as grain boundaries. Simulations show that as grain size decreases, the number of bonds formed, the W adh and its variability all increase, further supporting that interfacial covalent bond formation causes high adhesion. In some cases, sliding between delaminated MoS2 flakes during separation is observed, which further increases the W adh and the range of adhesive interaction. These results indicate that for low adhesion, the MoS2 grains should be large relative to the contact area to limit the opportunity for bonding, whereas small grains may be beneficial, where high adhesion is needed to prevent device delamination in flexible systems.
ISSN:1944-8244
1944-8252
DOI:10.1021/acsami.4c03208