Photo-Thermoelectric Effect at a Graphene Interface Junction

TL;DR

This study explores the photo-thermoelectric response at a graphene interface junction, revealing temperature-dependent behavior and thermal conductivity characteristics consistent with theoretical models.

Contribution

It demonstrates the photo-thermoelectric effect in graphene junctions and quantifies its temperature dependence, providing insights into graphene's thermal properties at cryogenic temperatures.

Findings

Photocurrent is driven by a photo-thermoelectric effect.

Photocurrent increases by a factor of ~10 at cryogenic temperatures.

Graphene's thermal conductivity follows a T^{1.5} dependence below 100 K.

Abstract

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.