There is an error in equation (1) of the above-named work [ibid., vol. 25, no. 3, Jun. 2015, Art. no. 2100707; doi: 10.1109/TASC.2014.2372673]. The corrected equation is provided. The difference is in the denominator, where 2βI should be replaced by 2 + βI .

We present thermal measurements of large area (over $1,000$~$\mu$m$^2$) monolayer graphene samples at cryogenic temperatures to study the electron-phonon thermal conductivity of graphene. By using two large samples with areas which differ by a factor of 10, we are able to clearly show the area dependence of the electron-phonon cooling. We find that, at temperatures far below the Bloch-Gruneisen temperature $T_\mathrm{BG}$, the electron-phonon cooling power is accurately described by the $T^4$ temperature dependence predicted for clean samples. Using this model, we are able to extract a value for the electron-phonon coupling constant as a function of gate voltage, and the graphene electron-lattice deformation potential. We also present results for thermal conductance at higher temperatures, above $T_\mathrm{BG}/4$, for which the clean limit no longer applies. In this regime we find a cooling power which is accurately described qualitatively, but not quantitatively, by a model which predicts the emission of very high energy phonons through a disorder-assisted mechanism.

We report the first calorimetric detection of individual He ∗ 2 excimers within a bath of superfluid 4 He. The detector used in this work is a single superconducting titanium transition edge sensor (TES) with an energy resolution of ∼ 1 eV, immersed directly in the helium bath. He ∗ 2 excimers are produced in the surrounding bath using an external gamma-ray source. These excimers exist either as short-lived singlet or long-lived triplet states. We demonstrate detection (and discrimination) of both states: in the singlet case the calorimeter records the absorption of a prompt ≈ 15 eV photon, and in the triplet case the calorimeter records a direct interaction of the molecule with the TES surface, which deposits a distinct fraction of the ≈ 15 eV, released upon decay, into the surface. We also briefly discuss the detector fabrication and characterization.

We report the first calorimetric detection of individual He∗2 excimers within a bath of superfluid 4He. The detector used in this work is a single superconducting titanium transition edge sensor (TES) with an energy resolution of ∼1 eV, immersed directly in the helium bath. He∗2 excimers are produced in the surrounding bath using an external gamma-ray source. These excimers exist either as short-lived singlet or long-lived triplet states. We demonstrate detection (and discrimination) of both states: In the singlet case the calorimeter records the absorption of a prompt ≈15 eV photon, and in the triplet case the calorimeter records a direct interaction of the molecule with the TES surface, which deposits a distinct fraction of the ≈15 eV, released upon decay, into the surface. We also briefly discuss the detector fabrication and characterization.

Luttinger liquid theory predicts that collective electron excitations due to strong electron-electron interactions in a one-dimensional (1D) system will result in a modification of the collective charge-propagation velocity. By utilizing a circuit model for an individual metallic single-walled carbon nanotube as a nanotransmission line, it has been shown that the frequency-dependent terahertz impedance of a carbon nanotube can probe this expected 1D Luttinger liquid behavior. We excite terahertz standing-wave resonances on individual antenna-coupled metallic single-walled carbon nanotubes. The terahertz signal is rectified using the nanotube contact nonlinearity, allowing for a low-frequency readout of the coupled terahertz current. The charge velocity on the nanotube is determined from the terahertz spectral response. Our measurements show that a carbon nanotube can behave as a Luttinger liquid system with charge-propagation velocities that are faster than the Fermi velocity. Understanding what determines the charge velocity in low-dimensional conductors is important for the development of next generation nanodevices.

We will present an analysis of the sensitivity and a preliminary design of a multiplexed THz direct detector array utilizing normal metal titanium (Ti) hot-electron nanobolometers (nano-HEB) as sensing elements. The readout technique employs direct reading of the electron temperature via a correspondent Johnson noise. In contrast to its superconducting transition-edge sensor (TES) counterpart, the normal-metal nano-HEB can operate within a very broad range of cryogenic temperatures (0.05 9 K) depending on the anticipated radiation background. The array does not require bias lines, 100s of nano-HEBs can be read by a single low-noise X-band amplifier via a filter bank channelizer. The modeling predicts that the Noise Equivalent Power (NEP) is fundamentally limited by the amplifier noise, with a NEP = 3 × 10 W/Hz expected at 50 mK.

We characterize the evolution of the electrical properties of ultra-thin niobium films stored in ambient conditions over a period of approximately seven months. Patterned films with thicknesses between 8 and 16 nm were fabricated via electron-beam deposition on unheated silicon substrates using a lift-off process. The film quality is similar to previous results obtained with sputter deposition onto unheated silicon substrates. The increase of the resistance and the decrease of the superconducting critical temperature are well described by an exponential function with a time constant of approximately 37 days.

We describe the properties of ultrasensitive graphene photon detectors for use in the far-infrared/terahertz spectral region and present theoretical predictions for their power detection sensitivity. These predictions are based on two graphene contacting schemes with superconducting contacts: contacts with a thin insulating barrier, and direct superconducting contacts. To quantitatively assess these predictions, we perform thermal measurements of graphene at low temperatures and analyse them to extract information on electron–phonon cooling in graphene. These new results for the electron–phonon cooling channel allow reliable prediction of the noise equivalent power (NEP) that can be expected from an optimized graphene detector, using measurement of the Johnson noise emission as the thermometry method. We find that an NEP of 2 × 10−19 W Hz−1/2 should be achievable under certain biasing conditions with an ideal device.

The sensitivity of a THz hot-electron nanobolometer (nano-HEB) made from a normal metal is analyzed. Johnson Noise Thermometry (JNT) is employed as a readout technique. In contrast to its superconducting TES counterpart, the normal-metal nano-HEB can operate at any cryogenic temperature depending on the required radiation background limited Noise Equivalent Power (NEP). It does not require bias lines; 100s of nano-HEBs can be read by a single low-noise X-band amplifier via a filter bank channelizer. The modeling predicts that even with the sensitivity penalty due to the amplifier noise, an NEP 10^-20 - 10^-19 W/Hz^1/2 can be expected at 50-100 mK in 10-20 nm thin titanium (Ti) normal metal HEBs with niobium (Nb) contacts. This NEP is fairly constant over a range of readout frequencies 10 GHz. Although materials with weaker electron-phonon coupling (bismuth, graphene) do not improve the minimum achievable NEP, they can be considered if a larger than 10 GHz readout bandwidth is required.

We characterize a single titanium (Ti) transition edge sensor (TES) designed for in situ detection of individual He2 excimers. We find a critical temperature of 420 mK, an electrothermal time constant of ~3 μs, and a total energy resolution of 1.5 eV. We observe the detector response to short laser pulses and present a successful analysis strategy for extracting direct-TES-hit pulses from a much larger background (due to substrate hits). We also present the response of a similar Ti TES with a built-in aperture designed to eliminate substrate background; this device has an energy resolution of better than 1.5 eV and a much reduced substrate signal. We discuss near-term plans for coupling multiple such TESs together with a shared aluminum (Al) absorber, increasing the He2 collection area to millimeter scales.

In this paper we give a detailed analysis of the expected sensitivity and operating conditions in the power detection mode of a hot-electron bolometer (HEB) made from a few μm2 of monolayer graphene (MLG) flake which can be embedded into either a planar antenna or waveguide circuit via NbN (or NbTiN) superconducting contacts with critical temperature ~ 14 K. Recent data on the strength of the electron-phonon coupling are used in the present analysis and the contribution of the readout noise to the Noise Equivalent Power (NEP) is explicitly computed. The readout scheme utilizes Johnson Noise Thermometry (JNT) allowing for Frequency-Domain Multiplexing (FDM) using narrowband filter coupling of the HEBs. In general, the filter bandwidth and the summing amplifier noise have a significant effect on the overall system sensitivity. The analysis shows that the readout contribution can be reduced to that of the bolometer phonon noise if the detector device is operated at 0.05 K and the JNT signal is read at about 10 GHz where the Johnson noise emitted in equilibrium is substantially reduced. Beside the high sensitivity (NEP < 10-20 W/Hz1/2), this bolometer does not have any hard saturation limit and thus can be used for far-IR sky imaging with arbitrary contrast. By changing the operating temperature of the bolometer the sensitivity can be fine tuned to accommodate the background photon flux in a particular application. By using a broadband low-noise kinetic inductance parametric amplifier, ~100s of graphene HEBs can be read simultaneously without saturation of the system output.

This article reviews recent research for development of sensitive graphene photon detectors in the infrared/far infrared/THz range. For this range, graphene has promising potential in thermal photon detectors. Graphene has ultra-small volume and low electron density, which gives relatively large heating per absorbed photon and fast response. At low temperatures the electron-phonon energy loss is small, so ultrasensitive power detection is possible. We review recent research on the science base of such detectors, and outline the major design challenges. Important factors that must be considered in making useful detectors include the photon and readout coupling efficiency, the method of electron temperature readout, and thermal isolation of the hot electrons.

The extremely small size of plasmonic antennas has made it difficult to integrate them with nanoscale detectors that require electrical leads, as the leads tend to degrade the resonant properties of the antenna. We present a design for integrating a plasmonic antenna with a nanoscale superconducting transition-edge sensor (TES) with electrical leads. Numerical simulations demonstrate high-efficiency coupling of 1550 nm incident photons into the sub-wavelength TES. Although we have chosen to design around a TES, this approach is broadly applicable to any dissipative nanoscale device that requires an electrical connection.

We report on noise and thermal conductance measurements taken in order to determine an upper bound on the performance of graphene as a terahertz photon detector. The main mechanism for sensitive terahertz detection in graphene is bolometric heating of the electron system. To study the properties of a device using this mechanism to detect terahertz photons, we perform Johnson noise thermometry measurements on graphene samples. These measurements probe the electron–phonon behavior of graphene on silicon dioxide at low temperatures. Because the electron–phonon coupling is weak in graphene, superconducting contacts with large gap are used to confine the hot electrons and prevent their out-diffusion. We use niobium nitride leads with a \(T_\mathrm {c}\approx 10\) K to contact the graphene. We find these leads make good ohmic contact with very low contact resistance. Our measurements find an electron–phonon thermal conductance that depends quadratically on temperature above 4 K and is compatible with single terahertz photon detection.

Noise equivalent power and time constant of a submillimeter wave hot-electron bolometer (HEB) made from monolayer graphene are analyzed using the lowest electron-phonon thermal conductance data reported to date. Frequency-domain multiplexed Johnson Noise Thermometry (JNT) is used for the detector readout. Planar microantennas or waveguides can provide efficient coupling of the graphene microdevice to radiation. The results show that the graphene HEB detector can be radiation background limited at very low level corresponding to the photon noise on a space telescope with cryogenically cooled mirror. Beside the high sensitivity, absence of a hard power saturation limit, higher operating temperature, and the ability to read 1,000s of elements with a single broadband amplifier will be the advantages of such a detector.

To achieve the state-of-the-art photon detectors, extensive research has been carried out on graphene-based bolometers. These utilize graphene’s promising properties including its small heat capacity, weak electron-phonon coupling, and small resistance. This article reviews the recent development of cryogenic graphene-based bolometers, which are of particular interest and importance for understanding as well as for taking advantage of the intrinsic properties of graphene. We summarize the major theoretical and experimental developments in the eld, including the phonon cooling mechanism and its dependence on temperature, doping, and disorder, and the experimental approaches for realizing bolometric detectors.We also estimate the ultimate performance of an ideal graphene bolometer as a power detector and a single-photon detector if superconducting contacts are employed. DOI 10.2478/gpe-2014-0001 Received August 20, 2013; accepted March 4, 2014. 1 Bolometer and device principles Modern photon detectors are widely employed in sensitive applications ranging from astrophysical observations to quantum communications [1–5]. The con gurations considered to date for ultrasensitive Terahertz graphene detectors are thermal detectors at low temperatures [6– 9], typically T ≤ 1 K [8, 10–13]. In this review article we consider such graphene photodetectors for the farinfrared (Terahertz) frequency range. Graphene detectors have been investigatedwith higher power signals from farinfrared to mid-infrared [14, 15] and in the near-IR to optical range [16, 17]. These other applications utilize dif*Corresponding Author: Xu Du: Department of Physics and Astronomy, Stony Brook University Daniel E. Prober: Departments of Applied Physics and Physics, Yale University Heli Vora: Department of Physics and Astronomy, Stony Brook University Christopher B. Mckitterick: Departments of Applied Physics and Physics, Yale University ferent detection modes for optimum sensitivity, including the photo-thermal-electric e ect, due to the much larger power or photon energy. Tode ne the challenges associatedwithphotondetection with graphene, in this section we outline the detector concepts and some of the graphene-related issues that are known, or that require further research. We then summarize the important performance metrics. An energy detector (calorimeter) works by absorbing a photon and reading out the resulting temperature increase. The schematic device structure of a thermal detector is shown in Figure 1. We show the detector element at the center of a planar antenna; although various antenna designs can be used. An antenna is needed because best sensitivity is achievedwith a small thermal detector, ofmicron size scale or smaller, whereas the photon wavelength is 100s of microns. The antenna allows e cient coupling of the photon to the small detector. Thermal single-photon detectors based on the superconductor transition provide good models of thermal detectors. These have been explored for energies ≥ 0.15 eV [5, 18] and studied extensively in the near-IR/visible range [4] and in the x-ray range [19]. A thermal detector can also be used tomeasure power, in which case it is called a bolometer. In the discussion below we will call both kinds of detectors ‘bolometers’. The bolometer as a power detector measures the di erence in the power absorbedwith the incoming beamon and o , as in Fig. 1. For linear operation, the response time is set, as in the calorimeter, by the speci c heat C and the thermal conductance G; τ = C/G. The thermal conductance is [8] G = Geph + Gdi + Gphoton