Thermal infrared emission reveals the Dirac point movement in biased graphene

TL;DR

This study demonstrates that thermal infrared emission from biased graphene can be used to map the Dirac point movement and carrier density distribution by analyzing temperature profiles via infrared spectroscopy.

Contribution

It introduces a novel method to visualize the Dirac point movement in graphene using thermal emission measurements under bias.

Findings

Thermal emission spectrum follows a grey body model with consistent emissivity.

Temperature distribution in graphene can be spatially mapped using infrared measurements.

The temperature maximum correlates with the Dirac point location and can be controlled by gate voltage.

Abstract

Graphene is a 2-dimensional material with high carrier mobility and thermal conductivity, suitable for high-speed electronics. Conduction and valence bands touch at the Dirac point. The absorptivity of single-layer graphene is 2.3%, nearly independent of wavelength. Here we investigate the thermal radiation from biased graphene transistors. We find that the emission spectrum of single-layer graphene follows that of a grey body with constant emissivity (1.6 \pm 0.8)%. Most importantly, we can extract the temperature distribution in the ambipolar graphene channel, as confirmed by Stokes/anti-Stokes measurements. The biased graphene exhibits a temperature maximum whose location can be controlled by the gate voltage. We show that this peak in temperature reveals the spatial location of the minimum in carrier density, i.e. the Dirac point.