Record Low Thermal Conductivity of Polycrystalline MoS2 films: Tuning the Thermal Conductivity by Grain Orientation

摘要

We report a record low thermal conductivity in polycrystalline MoS2 obtainedby varying grain sizes and orientations in ultrathin films. By optimizing thesulphurisation parameters of nanometre-thick Mo layer, we could grow MoS2 filmswith tuneable morphologies. The thermal conductivity is extracted from a Ramanlaser power-dependent study on suspended samples. The lowest value of thermalconductivity of 0.27 Wm-1K-1, which reaches a similar value as teflon, isobtained in a polycrystalline sample formed by a combination of horizontallyand vertically oriented grains, with respect to the bulk (001) monocrystal.Analysis by means of molecular dynamics and finite element method simulationsconfirm that such grain arrangement leads to lower grain boundary conductance.We discuss the possible use of these thermal insulating films in the context ofelectronics and thermoelectricity.