  Thermal conductivity measurement techniques for materials with nanoscale
dimensions require fabrication of very complicated devices or their
applicability is limited to a class of materials. Discovery of new methods with
high thermal sensitivity are required for the widespread use of thermal
conductivity measurements in characterizing materials properties. We propose
and demonstrate a simple non-destructive method with superior thermal
sensitivity to measure the in-plane thermal conductivity of nanosheets and
nanowires using the bolometric effect. The method utilizes laser beam heating
to create a temperature gradient, as small as a fraction of a Kelvin, over the
suspended section of the nanomaterial with electrical contacts. Local
temperature rise due to the laser irradiation alters the electrical resistance
of the device, which can be measured precisely. This resistance change is then
used to extract the temperature profile along the nanomaterial using thermal
conductivity as a fitting parameter. We measured the thermal conductivity of
V2O3 nanosheets to validate the applicability of the method and found an
excellent agreement with the literature. Further, we measured the thermal
conductivity of metallic 2H-TaS2 for the first time and performed ab initio
calculations to support our measurements. Finally, we discussed the
applicability of the method on semiconducting nanosheets and performed
measurements on WS2 and MoS2 thin flakes.
