Graphene and 2 dMaterials Open

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