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.more » « less
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- Scientific Reports
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The rate of energy transfer through soils is an important factor governing the active layer (seasonal thaw layer) in polar regions. Energy is transferred through conductive and convective means, which are primarily influenced by the bulk density and water content of soils. With global temperatures changing, it becomes important to understand how soil properties influence heat transfer and active layer depths in climatically sensitive regions, such as the Antarctic Peninsula. In this study we analyzed conductive energy transfer through several soil types on Amsler Island and Cierva Point in the central region of the western Antarctic Peninsula. Active layer temperatures on Amsler Island were monitored every three hours using iButton thermistors installed at regular depth intervals down to 2 m. Soil textures were loamy to sandy with water contents between 5 and 27%. Freezing and thawing transmission rates for all soils ranged from 1.4 to 6.9 cm/day. Thermal transmission rates were fastest in sandy soils with low water contents, indicating that the large, interconnected pores of the sandy soils facilitated the quick movement of heat with water flow through the soil profile. Snow accumulation differences also played a significant role on winter thermal propagation by providing a thermal barrier between the ground surface and atmosphere. Although there was a wide range in thermal transmission among the soils, active layer depths had little variation (7.8–9.7 m). This consistency derives from the greater dependence of very thick active layers on long‐term climatic conditions rather than on soil properties. The presence of thick moss significantly slowed thermal transmission and decreased active layer thicknesses. These effects primarily are due to the high heat capacity of water and air retained within the moss, slowing thermal transmission rates, acting as a thermal buffer between atmospheric conditions and the underlying soils. Copyright © 2016 John Wiley & Sons, Ltd.