Abstract
While terahertz spectroscopy can provide valuable information regarding the charge transport properties in semiconductors, its application for the characterization of low-conductive two-dimensional layers, i.e., σs < < 1 mS, remains elusive. This is primarily due to the low sensitivity of direct transmission measurements to such small sheet conductivity levels. In this work, we discuss harnessing the extraordinary optical transmission through gratings consisting of metallic stripes to characterize such low-conductive two-dimensional layers. We analyze the geometric tradeoffs in these structures and provide physical insights, ultimately leading to general design guidelines for experiments enabling non-contact, non-destructive, highly sensitive characterization of such layers.
Highlights
While terahertz spectroscopy can provide valuable information regarding the charge transport properties in semiconductors, its application for the characterization of low-conductive twodimensional layers, i.e., σs < < 1 mS, remains elusive
With the advent of 2D materials, such as graphene and transition metal dichalcogenides (TMDCs), as well as recent progress on two-dimensional sheet charges in semiconductor heterostructures, terahertz spectroscopy of two-dimensional layers has become a topic of particular interest, e.g., Refs.[3,6,7,8,9,10]
The sheet conductivity extracted from terahertz measurements would be a spatially averaged nanoscale conductivity and is minimally affected by microscale scattering phenomena that would play a role in direct current (DC) transport measurements wherein the carrier transport is typically probed over length scales that are three orders of magnitude larger
Summary
While terahertz spectroscopy can provide valuable information regarding the charge transport properties in semiconductors, its application for the characterization of low-conductive twodimensional layers, i.e., σs < < 1 mS, remains elusive This is primarily due to the low sensitivity of direct transmission measurements to such small sheet conductivity levels. In order to be able to characterize the transport properties of such low-conductive two-dimensional layers through terahertz spectroscopy, alternative approaches to direct transmission or reflection spectroscopy must be employed In this regard, there have been prior works on utilizing parallel-plate waveguide (PPWG) geometries for enhancing this s ensitivity[21,22]. A structure operating in a simple transmission geometry would be very convenient wherein a normally incident beam has its electric field in the plane of the two-dimensional sheet charge
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