Spatial mapping of the thermal conductivity of graphene by an opto-thermal method*

Graphene’s thermal properties are extraordinary, with a predicted thermal conductivity (κ) of 5’000 W/(mK). However, the reported experimental values show variations of one order of magnitude, ranging from 500 to 5’000 W/(mK), with large experimental uncertainties. To overcome these issues, we propose a novel approach to spatially resolve the thermal conductivity of suspended graphene membranes, combining Raman microscopy with finite element method (FEM) calculations. In our method, temperature maps of the graphene membranes are obtained from the shift of the 2D Raman peak with temperature. These maps are then used as input for FEM calculations to extract the corresponding thermal conductivity maps. Moreover, we demonstrate that the thermal conductivity of graphene can be locally tuned in a controlled manner by introducing defects using the focused ion beam technique. This approach paves the way to investigate the thermal properties of other layered materials.