▎ 摘　　要

We directly image hot spot formation in functioning mono and bilayer graphene field effect transistors (GFETs) using infrared thermal microscopy Correlating with an electrical-thermal transport model provides insight into carrier distributions fields and GFET power dissipation The hot spot corresponds to the location of minimum charge density along the GFET by changing the applied bias this can be shifted between electrodes or held in the middle of the channel in ambipolar transport Interestingly the hot spot shape bears the imprint of the density of states in mono- vs bilayer graphene More broadly we find that thermal imaging combined with self consistent simulation provide a noninvasive approach for more deeply examining transport and energy dissipation in nanoscale devices