Photo-Thermoelectric Effect at a Graphene Interface Junction

We investigate the optoelectronic response of a graphene single-bilayer interface junction using phococurrent (PC) microscopy. We measure the polarity and amplitude of the PC while varying the Fermi level by tuning a gate voltage. These measurements show that the generation of PC is by a photothermoelectric effect. The PC displays a factor of similar to 10 increase at the cryogenic temperature as compared to room temperature. Assuming the thermoelectric power has a linear dependence on the temperature, the inferred graphene thermal conductivity from temperature dependent measurements has a T-1,T-5 dependence below similar to 100 K, which agrees with recent theoretical predictions.