Dual-gated bilayer graphene hot electron bolometer

Detection of infrared light is central to diverse applications in security, medicine, astronomy, materials science, and biology. Often different materials and detection mechanisms are employed to optimize performance in different spectral ranges. Graphene is a unique material with strong, nearly frequency-independent light-matter interaction from far infrared to ultraviolet, with potential for broadband photonics applications. Moreover, graphene's small electron-phonon coupling suggests that hot-electron effects may be exploited at relatively high temperatures for fast and highly sensitive detectors in which light energy heats only the small-specific-heat electronic system. Here we demonstrate such a hot-electron bolometer using bilayer graphene that is dual-gated to create a tunable bandgap and electron-temperature-dependent conductivity. The measured large electron-phonon heat resistance is in good agreement with theoretical estimates in magnitude and temperature dependence, and enables our graphene bolometer operating at a temperature of 5 K to have a low noise equivalent power (33 fW/Hz1/2). We employ a pump-probe technique to directly measure the intrinsic speed of our device, >1 GHz at 10 K.Comment: 5 figure

Social Relationships and Mortality Risk: A Meta-analytic Review

In a meta-analysis, Julianne Holt-Lunstad and colleagues find that individuals' social relationships have as much influence on mortality risk as other well-established risk factors for mortality, such as smoking

P-Type Epitaxial Graphene on Cubic Silicon Carbide on Silicon for Integrated Silicon Technologies

Copyright © 2019 American Chemical Society. The synthesis of graphene on cubic silicon carbide on silicon pseudosubstrates draws enormous interest due to the potential integration of the 2D material with the well-established silicon technology and processing. However, the control of transport properties over large scales on this platform, essential for integrated electronics and photonics applications, has lagged behind so far, due to limitations such as 3C-SiC/Si interface instability and nonuniform graphene coverage. We address these issues by obtaining an epitaxial graphene (EG) onto 3C-SiC on a highly resistive silicon substrate using an alloy-mediated, solid-source graphene synthesis. We report the transport properties of EG grown over large areas directly on 3C-SiC(100) and 3C-SiC(111) substrates, and we present the corresponding physical models. We observe that the carrier transport of EG/3C-SiC is dominated by the graphene-substrate interaction rather than the EG grain size, sharing the same conductivity and same inverse power law as EG on 4H- or 6H-SiC(0001) substrates - although the grain sizes for the latter are vastly different. In addition, we show that the induced oxidation/silicates at the EG/3C-SiC interface generate a p-type charge in this graphene, particularly high for the EG/3C-SiC(001). When silicates are at the interface, the presence of a buffer layer in the EG/3C-SiC(111) system is found to reduce somewhat the charge transfer. This work also indicates that a renewed focus on the understanding and engineering of the EG interfaces could very well enable the long sought-after graphene-based electronics and photonics integrated on silicon

Correlation-induced single-flux-quantum penetration in quantum rings

Contains fulltext : 83667.pdf (publisher's version ) (Closed access)5 p

Capital mobility and labor market volatility

Capital mobility, Efficiency wages, Labor market volatility, E44, F36, F41,

Possible Chemical Transformations in Snow and Ice Induced by Solar (UV PHOTONS) and Cosmic Irradiation (MUONS)

Over the last decade there has been a growing interest in the chemical composition of the snow packs in the polar regions (Bales and Wolff, 1995). Delmas (Delmas, 1992; Delmas, 1994) has noted that “information recorded in polar ice cores over the last several hundred millennia is invaluable to studies aimed at understanding the pre-industrial environmental system and anticipating the future evolution of the climate and the atmosphere.” For example, the isotopic composition of the ice (H_2O) matrix is a reliable paleothermometer. From the analysis of deep Antarctic and Greenland ice cores the ice age environmental conditions appeared to correspond to about 6 °C cooler temperatures and atmospheric CO_2 and CH_4 levels lower by factors of nearly 2 and 4, respectively. The biogeochemical cycles of S and N also appear to be affected by climatic changes that result in modifications in the source intensity and the transport of gaseous precursors. Even though atmospheric sulfate is derived principally from marine biogenic sources (i.e., dimethyl sulfide emission), cataclysmic volcanic eruptions can contribute sporadically to the atmospheric sulfur budget through large point source emissions of SO_2. These events are ultimately detected in polar ice as H_2SO_4 spikes. Nitrate, which is the next most abundant anion found in polar snowfall, exhibits concentration changes that are poorly understood, but which could be linked with the polar ozone hole formation. In addition to ions derived primarily from gas-to-particle conversions, continental dust and sea-spray aerosol components are also present in the ice at much higher concentrations during ice ages than during interglacial periods due to an intensification of their production and long range transport under glacial climatic conditions