We investigate the optoelectronic response of a graphene interface junction, formed with bilayer and single-layer graphene, by photocurrent (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 photo-thermoelectric effect. The PC displays a factor of ~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^{1.5} dependence below ~100 K, which agrees with recent theoretical predictions.
@article{arxiv.0907.3173,
title = {Photo-Thermoelectric Effect at a Graphene Interface Junction},
author = {Xiaodong Xu and Nathaniel M. Gabor and Jonathan S. Alden and Arend van der Zande and Paul L. McEuen},
journal= {arXiv preprint arXiv:0907.3173},
year = {2015}
}