Abstract
We demonstrate a method for reliably determining the electrical properties of graphene including the carrier scattering time and carrier drift mobility from terahertz time- domain spectroscopy measurements (THz-TDS). By comparing transients originating from directly transmitted pulses and the echoes from internal reflections in a substrate, we are able to extract electrical properties irrespective of random time delays between pulses emitted in a THz-TDS setup. If such time delays are not accounted for they can significantly influence the extracted properties of the material. The technique is useful for a robust determination of electrical properties from THz-TDS measurements and is compatible with substrate materials where transients from internal reflections are well-separated in time.
Highlights
Terahertz time-domain spectroscopy (THz-TDS) is a non-contact measurement technique that can be used to determine electrical properties of conducting thin films such as graphene [1,2,3,4]
Non-gated rapid spatial mapping of the carrier drift mobility and carrier density (Ns) of graphene by THz-TDS was recently reported [5], which presents a step forward compared to earlier reports that mainly gauges the conductivity [6,7] or extracts the mobility through back-gated THz-TDS measurements requiring special substrates [8,9]
THz-TDS mapping measurements were conducted on graphene films
Summary
Terahertz time-domain spectroscopy (THz-TDS) is a non-contact measurement technique that can be used to determine electrical properties of conducting thin films such as graphene [1,2,3,4]. An accurate and reliable determination of the electrical properties of graphene is required for THz-TDS to become an industry standard for rapid in-line characterization. The electrical properties extracted from such fits were found to vary significantly depending on the choice of reference point on a sample. We attribute those point to point variations to time shifts (timing jitter and drift) between individual pulses transmitted in the setup. We show a method for reliably extracting electrical properties from graphene by comparing the information that is available from transients that are directly transmitted through the substrate and transients originating from internal reflections in the substrate
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