Investigation of the Layer and Substrate Dependency of the Thermal Conductivity of MoS2

20th International Nanoscience and Nanotechnology Conference (NanoTR-20), İzmir, Turkey, 26 - 28 August 2026, pp.431, (Summary Text)

In recent years, two-dimensional (2D) transition metal dichalcogenides (TMDs) have gained attention as promising candidates for

thermoelectric applications. Their layered structures and high surface-to-volume ratios inherently lead to low thermal conductivity and

improved thermoelectric performance compared to bulk materials. In this context, understanding how heat is transported in 2D TMDs is

essential for evaluating their potential in thermoelectric and nanoelectronic devices.

In this study, the thermal response of mechanically exfoliated MoS2 flakes with different layer numbers was investigated on SiO2/Si, Si3N4

membrane and PDMS substrates using optothermal Raman spectroscopy. The layer numbers of the samples were determined by

photoluminescence (PL) measurements and atomic force microscopy (AFM). Temperature-dependent Raman measurements were performed

to obtain the first-order temperature coefficients of the E1

2g and A1gphonon modes, while laser power-dependent Raman measurements were

used to evaluate local heating effects.

The thermal conductivity/effective thermal conductivity values were obtained from the Raman peak shifts induced by changes in temperature

and laser powerThe highest thermal conductivity was observed for 1L MoS2 on the SiO2/Si substrate, with a value of 63.5 W m−1.K−1, while

the values decreased to 27.5 and 22.8 W m−1 K−1 for 4L and bulk MoS2, respectively.On the Si3N4 membrane values were obtained as 22.5,

23.4 and 37.8 W m−1.K−1, while on the PDMS substrate were obtained as 20.8, 22.3 and 25.9 W m−1.K−1 for 1L, 4L and bulk MoS2,

respectively.

The results showed that the thermal transport behavior of MoS2 strongly depends on both the substrate material and the layer number. For

monolayer MoS2, the highest thermal conductivity was obtained on the SiO2/Si substrate, while lower values were observed on Si3N4 and

PDMS substrates. This difference was mainly attributed to exciton–phonon coupling, which may preserve phonon coherence, rather than to the

direct thermal effect of the substrate.In addition, the change in layer number caused noticeable variations in the thermal conductivity values,

indicating that phonon transport in MoS2 is affected by both layer-dependent structural properties and substrate coupling.

These findings demonstrate that the thermal conductivity of 2D materials is not only affected by the thermal properties of the substrates, but is

also influenced by the strength of exciton–phonon coupling.