Abstract
Thermal conductivity of two-dimensional (2D) materials is of interest for energy storage, nanoelectronics and optoelectronics. Here, we report that the thermal conductivity of molybdenum disulfide can be modified by electrochemical intercalation. We observe distinct behaviour for thin films with vertically aligned basal planes and natural bulk crystals with basal planes aligned parallel to the surface. The thermal conductivity is measured as a function of the degree of lithiation, using time-domain thermoreflectance. The change of thermal conductivity correlates with the lithiation-induced structural and compositional disorder. We further show that the ratio of the in-plane to through-plane thermal conductivity of bulk crystal is enhanced by the disorder. These results suggest that stacking disorder and mixture of phases is an effective mechanism to modify the anisotropic thermal conductivity of 2D materials.
Highlights
Thermal conductivity of two-dimensional (2D) materials is of interest for energy storage, nanoelectronics and optoelectronics
The thermal conductivity of single, few-layer and bulk MoS2 has been reported recently, the effects of structural and compositional disorder on the anisotropic thermal conductivity of layered materials, which usually occurs during crystal growth, fabrication and applications, have not yet been systematically characterized[6,7,8]
Our analysis suggest that the enhanced thermal anisotropy ratio in LixMoS2 bulk crystal is likely due to the combination of phonon-focusing effects and pronounced differences in the inplane and through-plane length scale of the lithiation-induced disorder
Summary
Thermal conductivity of two-dimensional (2D) materials is of interest for energy storage, nanoelectronics and optoelectronics. We further show that the ratio of the in-plane to through-plane thermal conductivity of bulk crystal is enhanced by the disorder These results suggest that stacking disorder and mixture of phases is an effective mechanism to modify the anisotropic thermal conductivity of 2D materials. The thermal conductivity of single, few-layer and bulk MoS2 has been reported recently, the effects of structural and compositional disorder on the anisotropic thermal conductivity of layered materials, which usually occurs during crystal growth, fabrication and applications (for example, in energy storage, thermoelectrics and nanoelectronics), have not yet been systematically characterized[6,7,8]. Our most striking observation is that the thermal anisotropy ratio in bulk LixMoS2 crystals increases from 52 (x 1⁄4 0) to 110 (x 1⁄4 0.34) as a result of lithiation-induced stacking disorder and phase transitions. Our analysis suggest that the enhanced thermal anisotropy ratio in LixMoS2 bulk crystal is likely due to the combination of phonon-focusing effects and pronounced differences in the inplane and through-plane length scale of the lithiation-induced disorder
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