Dynamic interfacial mechanical–thermal characteristics of atomically thin two-dimensional crystals

Abstract

Owing to the flexible nanoelectronic applications of two-dimensional (2D) materials, further exploration of their nanoscale local mechanical properties and their coupled physical characteristics becomes extremely significant. The puckering effect is a typical micro/nanoscale local frictional characteristic generally in the tip-film-substrate system, which is simultaneously expected to be coupled with a dynamic thermal interfacial response. Here, applying scanning thermal microscopy (SThM), we observed a novel mechanical-thermal coupling effect in monolayer/bilayer MoS2 and WS2 films: puckering deformation can induce the enhancement of interfacial thermal resistance (TR). By the SThM method, the puckering effect was further proved to depend on the film thickness and the scan velocity. More importantly, the crystallographic orientation-dependent anisotropy of the puckering effect in atomically thin two-dimensional crystals was demonstrated by SThM. It is inferred that the puckering deformation of the film redistributes the in-plane stress, resulting in the isotropy breaking of the in-plane stiffness. Such new findings are of great significance to help optimize the nanoscale tribological/thermal design and dynamic mechanical-thermal management of 2D-materials in nanoelectronics.

Advanced atomic force microscopies and their applications in two-dimensional materials: a review

“…Scanning thermal microscopy (SThM) [120,121] can quantitatively map temperature fields or thermal properties by scanning a sharp SThM probe with a temperature sensor at the tip. This technique has been applied in diverse areas, including microelectronics [122][123][124], optoelectronics [125,126], carbon nanotubes [127,128], and 2D material [53], since the 1990s.…”

“…The electric resistance of the probe is thermosensitive, and the relationship of the electric resistance (R probe ) versus temperature (∆T probe = T probe -T air ) is shown in figure 13(d). The maximum electric resistance is observed at 550 • C. Below 550 • C, the electric resistance of the probe corresponds to a specific temperature, as follows [53]:…”

“…Special physical phenomena could be observed when applying SThM. Xu et al [53] observed a novel mechanicalthermal coupling effect in monolayer/bilayer MoS 2 , and WS 2 films; essentially, puckering deformation can enhance interfacial TR (figure 38). Figure 38(a) shows the FFM images of monolayer/bilayer MoS 2 with increasing normal forces.…”

In Situ Detection of Local Structure Transformation of 2D SnSe Nanosheets through Nanothermomechanical Behavior

“…Fortunately, the atomic force microscope (AFM) provides a multiphysical field coupling platform to probe the local mechanical, electronic, thermal, and other physical behavior on a nanoscale level. [10][11][12] The mechanical detection is especially sensitive to tuning the temperature-dependent structure and properties under an artificially controlled field.…”

Toplayer-dependent crystallographic orientation imaging in the bilayer two-dimensional materials with transverse shear microscopy

“…Nanomechanical deformation has been extensively investigated by the atomic force microscopy (AFM) indentation experiments on suspended films. [21][22][23] Based on AFM platform, [24][25][26][27] friction force microscopy (FFM) and transverse shear microscopy (TSM), as the derivative mode of contact AFM, [28][29][30][31][32] now have been widely used to study the elastic deformation, 19,31 crystal structure, 28 surficial ripples of 2D materials 8,34,35 and so on. Such studies have revealed an important phenomenon in which nanomechanical contact behavior could be dependent on the number of layers and substrates.…”