Subwavelength THz imaging of graphene photoconductivity

TL;DR

This paper demonstrates subwavelength THz imaging of graphene's ultrafast photoconductivity, revealing spatial inhomogeneities correlated with electron density variations, which are crucial for improving device fabrication.

Contribution

It introduces a method for high-resolution imaging of graphene's photoconductivity and correlates inhomogeneities with doping density variations.

Findings

Subwavelength resolution of 75 μm achieved in THz imaging.

Strong correlation between photoconductivity inhomogeneities and electron density.

Highlights importance of uniform doping in graphene fabrication.

Abstract

Using a spatially structured, optical pump pulse with a THz probe pulse, we are able to determine spatial variations of the ultrafast THz photoconductivity with sub-wavelength resolution (75 $\mu m \approx \lambda/5$ at 0.8 THz) in a planar graphene sample. We compare our results to Raman spectroscopy and correlate the existence of the spatial inhomogeneities between the two measurements. We find a strong correlation with inhomogeneity in electron density. This demonstrates the importance of eliminating inhomogeneities in doping density during CVD growth and fabrication for photoconductive devices.