Influence of stacking disorder on cross-plane thermal transport properties in TMPS3 (TM = Mn, Ni, Fe)

Abstract

We investigated the thermal transport properties of magnetic van der Waals materials, TMPS3 (TM = Mn, Ni, and Fe), using the time-domain thermoreflectance technique. We determined the cross-plane thermal conductivity, which turns out to be relatively low, i.e., about 1 W m−1 K−1 for all TMPS3 investigated. When compared with previous results of graphite and transition metal dichalcogenides (TMDs), thermal conductivity becomes smaller as it goes from graphite to TMDs to TMPS3, and the difference is larger at low temperature, e.g., around 50 K. From the Callaway model analysis, we could attribute the large thermal conductivity reduction for TMPS3, particularly at low temperature, to the phonon scattering from the boundary. We actually confirmed the existence of the large population of the stacking faults with the cross-sectional transmission electron microscopy image of MnPS3. This suggests that intrinsic or extrinsic stacking faults formed in van der Waals materials and their heterostructures can play an important role in reducing the cross-plane thermal conductivity as a source of the boundary scattering.

Order-Determined Structural and Energy Transport Dynamics in Solid-Supported Interfacial Methanol

“…Second, both 2D-layered and 3D-ordered methanol assemblies have intralayer hydrogen bonds and cross-plane vdW interactions, although an in-plane domain size effect is anticipated for the former, and the latter between the two structures may likely have a small difference in energy per molecule. Two scenarios are possible to account for the observed difference in the mode of energy transport: (i) coherent cross-plane propagation or noncoherent diffusion is highly dependent on the lateral domain size, in that a more extended layer with many more methanol molecules favors synchronized movements whereas smaller domains with structural disorders in the boundaries disrupt coherent motions; (ii) compared to the 3D crystalline structure, the disorder and azimuthal rotation in the stacking of 2D-layered assemblies cause strong scattering or trapping of cross-plane energy-carrying phonons, resulting in a significant reduction in the transport speed and phenomenologically a different mode of energy transfer because of localization of the nonpropagating vibrational modes. , It may also be possible that both scenarios contribute to our observations.…”

“…Generally speaking, amorphous or glassy solids have low thermal conductivities compared to their crystalline counterparts because of the strong localization nature of heat carriers as a result of disordered structures. , In contrast, a well-ordered crystalline structure has delocalized propagating modes to contribute to a higher thermal conductivity . However, the situation may be less apparent when both order and disorder (or misfits) are present in a solid, which becomes relevant in vdW materials and heterostructures. − In the WSe 2 studies mentioned earlier, a multilayered solid with disorder in the stacking exhibits a much lower cross-plane thermal conductivity compared to a well-stacked crystalline one. , Reduced thermal conductivities were also reported in another study of multicomponent layered materials with structural misfits …”

Structural and Chemical Modifications of Few-Layer Transition Metal Phosphorous Trisulfides by Electron Irradiation

“…At the same time, TMPTs have not yet been intensively analyzed experimentally to understand defect-induced properties, although the theoretical studies on single layers predicted intriguing defect-induced changes in the electronic and magnetic properties of the materials, for examples, the inclusion of spin-split mid-gap states in MnPS 3. Furthermore, in several studies, − stacking faults were reported for various bulk TMPTs, and it was shown that the properties (i.e., thermal conductivity) of the materials are strongly altered by these defects; , however, no detailed studies on the effect of these faults on few-layer systems are given in the literature.…”