  The thermophysical properties of supported and free-standing nanomaterials
would be different due to the substrate effect. To determine the thermophysical
properties of supported 2D nanomaterials, this paper developed a two-step
dual-wavelength flash Raman (DFR) mapping method. The thermal conductivity of
the supported 2D nanomaterial and the thermal contact conductance between the
sample and the substrate can be determined by steady-state step. And then the
thermal diffusivity of the sample can be characterized by the transient step.
Two models are also proposed in this paper. When the substrate temperature
rises obviously, a full model considered the substrate temperature distribution
is used to decouple the thermal diffusivity, thermal conductivity, and the
thermal contact conductance. When the maximum substrate temperature rise is
less than 20% of the maximum sample temperature rise, the temperature
distribution and variation of the substrate is assumed proportionate to the
sample, and then a simplified model can be used to analyse the thermal
diffusivity and the other parameters. For the thermal diffusivity, the system
error caused by simplifying assumptions is less than 1%, when a dimensionless
parameter related to the thermal contact conductance and the thermal
conductivity less than 1 and the maximum temperature rise of the substrate less
than 15% of that of the supported sample.
