Subwavelength Terahertz Imaging of Graphene Photoconductivity
Nano Letters: a journal dedicated to nanoscience and nanotechnology
American Chemical Society
Using a spatially structured, optical pump pulse with a terahertz (THz) probe pulse, we are able to determine spatial variations of the ultrafast THz photoconductivity with subwavelength resolution (75 μm ≈ λ/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.
This research has been supported by the European Commission (FP7-ICT-2013-613024-GRASP) and EPSRC fellowship (EP/K041215/1). R.I.S. acknowledges support from QinetiQ and EPSRC under iCase award 12440575. The authors would like to thank Dr. Eugene Alexeev for very useful discussions, Nick Cole for technical assistance, and Nick Stone for the use of his spectrometer.
This is the author accepted manuscript. The final version is available from American Chemical Society via the DOI in this record.
Published online 13 October 2016