Thermal properties of thin films made from MoS2 nanoflakes and probed via statistical optothermal Raman method

Abstract

A deep understanding of the thermal properties of 2D materials is crucial to their implementation in electronic and optoelectronic devices. In this study, we investigated the macroscopic in-plane thermal conductivity (κ) and thermal interface conductance (g) of large-area (mm2) thin film made from MoS2 nanoflakes via liquid exfoliation and deposited on Si/SiO2 substrate. We found κ and g to be 1.5 W/mK and 0.23 MW/m2K, respectively. These values are much lower than those of single flakes. This difference shows the effects of interconnections between individual flakes on macroscopic thin film parameters. The properties of a Gaussian laser beam and statistical optothermal Raman mapping were used to obtain sample parameters and significantly improve measurement accuracy. This work demonstrates how to address crucial stability issues in light-sensitive materials and can be used to understand heat management in MoS2 and other 2D flake-based thin films.

Thermal Sensitive Quantum and Phonon Confinement in Semiconducting Triangular-Shaped MoS2

“…We have found the value of g ∼ 1.264 ± 0.128 MW m –2 K –1 and k s ∼ 42 ± 8 W m –1 K –1 by solving MATLAB program. In literature, it has been observed that the mono- or multilayer MoS 2 shows the values of interfacial thermal conductance “ g ” from 0.1 to 14 MW m –2 K –1 , and low “ g ” values are found by the Raman optical thermometry method compared to other methods like the electrical thermometry method. ,,− In the present work, we found the value of “ g ” around 1.264 ± 0.128 MW m –2 K –1 for triangular bilayer MoS 2 over the SiO 2 /Si substrate. The interfacial coupling may be affected by lattice mismatch between MoS 2 and substrate .…”

Phonon and Thermal Properties of Thin Films Made from WS2 Mono- and Few-Layer Flakes

“…Now we turn our attention toward the estimation of thermal conductivity and thermal interface conductance of WS 2 thin film on SiO 2 substrate. To do so, we used the well-established optothermal Raman technique, which studies phonon response to global heating and local laser heating. , The details of the experimental and theoretical basis of this method can be found in our previous works and Supporting Information. , In brief, during the Raman experiment, we can increase the temperature of the sample by laser illumination. The temperature increase is dependent on power input and distribution.…”

“…In the end, we point out that results presented here are part of a larger trend as similar results were shown for graphene and MoS 2 , where the films produced from nanoflakes have also at least 1 order of magnitude smaller thermal conductivity than their monocrystalline bulk and monolayer counterparts (see Table ). , Such results can be useful in managing the heat in future applications of thin film and bring new insights into proper device optimization and design.…”

“…25,26 The details of the experimental and theoretical basis of this method can be found in our previous works and Supporting Information. 23,27 In brief, during the Raman experiment, we can increase the temperature of the sample by laser illumination. The temperature increase is dependent on power input and distribution.…”

Induced 2H-Phase Formation and Low Thermal Conductivity by Reactive Spark Plasma Sintering of 1T-Phase Pristine and Co-Doped MoS2 Nanosheets

“…57,58 Some recent papers report thermal conductivities below 1 W/m•K in polycrystalline thin films with a record lowest value of 0.27 W/m•K reported on polycrystalline films with perfect controlled grain orienta-tion. 38,59,60 Experimentally, the out-of-plane thermal conductivity of bulk MoS 2 at 300 K is reported with values in a common range of 2.2−6.1 W/m•K and the lowest value of 1.05 W/m•K has been reported in restacked compounds with a similar 2H phase in the room temperature range. 28,49,61 This current state of the art ranks our samples in the lowest range of MoS 2 thermal conductivity ever reported.…”