Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session D30: Focus Session: Graphene Devices: Fabrication, Characterization and Modeling: Optoelectronic Properties |
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Sponsoring Units: DMP Chair: Marco Nardelli, University of North Texas Room: 605 |
Monday, March 3, 2014 2:30PM - 2:42PM |
D30.00001: Electrically tunable optical emitter graphene coupling Lucas Orona, Klaas-Jan Tielrooij, Frank Koppens, Pablo Jarillo-Herrero Graphene exhibits both novel electronic and optical properties. Optical emitters near graphene experience non-radiative coupling that generates electron hole pairs in the graphene. We are able to vary the strength of this coupling by electrically gating the graphene. Strong gating raises the Fermi energy so that no more electrons can be excited by the emitters, essentially halting the non-radiative decay. My talk will be about experimental measures of this process, which we call Pauli blocking. [Preview Abstract] |
Monday, March 3, 2014 2:42PM - 2:54PM |
D30.00002: Large and Tunable Optical Absorption in Quasi-Periodically Corrugated Graphene Guang-Xin Ni, De Lima Ferreira Rodrigues Ma, Henrik Andersen, Seung-Jae Baeck, Jong-Hyun Ahn, Viana-Gomes Jose Carlos, Vitor M. Pereira, Castro Neto Antonio Helio, Barbaros \"Ozyilmaz Graphene is currently one of the notable players in the intense drive towards bendable, thin, and portable electronic displays. Given that the intrinsic transparency of a graphene monolayer is 97.7{\%}, any reproducible and controllable modulation of transparency can have a significant impact for graphene as a viable transparent conducting electrode. Here we demonstrate a large and tunable optical aborption modulation in large-scale CVD graphene by introducing quasi-periodic ripples using functional elastomer substrates. We find that the optical modulation is more than 15{\%} at visible wavelengths and moreover such optical modulation can be simultaneously tuned on and off by controlling the elastomer status. The simple device configuration and large tunability optical response of graphene demonstrated in this study can be very important towards novel ultra-thin optical polarizer devices applications. [Preview Abstract] |
Monday, March 3, 2014 2:54PM - 3:06PM |
D30.00003: Tunable Photocurrent and Photoresponsivity of Graphene/Silicon Carbide Field Effect Photodetectors Biddut K. Sarker, Isaac Childres, Edward Cazalas, Igor Jovanovic, Yong P. Chen Graphene is a promising material for a variety of optoelectronics applications due to its unique electronic and optical properties. In this talk, we present detailed photoresponse studies of a novel photodetector based on graphene field effect transistors on undoped silicon carbide substrates. We show that the photocurrent of our devices under 400 nm laser illumination is positive (negative) for a negative (positive) back gate-voltage and almost zero for zero gate-voltage. For a fixed gate-voltage, the photocurrent and photoresponsivity can be tuned by the power of the light, source-drain bias-voltage and the position of the laser beam on the devices. We propose that the photodetection mechanism of our devices relies on the high sensitivity of the resistivity of graphene to the local change of the electric field that can result from photoexcited carriers produced in the underlying semiconductor substrates. [Preview Abstract] |
Monday, March 3, 2014 3:06PM - 3:18PM |
D30.00004: ABSTRACT WITHDRAWN |
Monday, March 3, 2014 3:18PM - 3:30PM |
D30.00005: Magnetic Field Effects of Light Scattering from Fluorinated Multi-Layer Graphene Flakes in Ground and Excited States Suspended in Organic Solvents Bin Hu, Lei He, Mingxing Li, Zheng Gai, Augustine Urbas Magnetic field effect of light scattering (MFELS) can be developed by magnetic polarization-induced alignment of magnetic nanoparticles suspended in liquid states. The MFELS can reflect the magnetic polarization in ground and excited states, when an external photoexcitation is applied, and the magnetoelectric coupling, when the host solvent is changed with a different dielectric constant, in magnetic nanoparticles. We report a giant MFELS with a magnitude over 80 {\%} from fluorinated multi-layer graphene (FG) suspended in organic solvents. Applying a magnetic field (\textless 900 mT) can remarkably increase the light scattering intensity from the suspended FG flakes. This indicates that a magnetic field can cause an alignment of suspended FG flakes due to anisotropic magnetic polarization effects. We find that increasing the dielectric constant of host solvent can largely enhance the MFELS magnitude. This phenomenon implies that the electrical polarization is intrinsically coupled with the magnetic polarization in the FG flakes, suggesting a new mechanism for magnetoelectric coupling. Furthermore, we show that a photoexcitation can lead to an enhancement on the MFELS magnitude from the suspended FG flakes. This indicates that the excited states can generate a stronger magnetic polarization through magnetoelectric coupling in the suspended FG flakes. [Preview Abstract] |
Monday, March 3, 2014 3:30PM - 3:42PM |
D30.00006: Spaser with graphene nanoribbon Oleg Berman, Roman Kezerashvili, Yurii Lozovik A novel type of spaser with the net amplification of surface plasmons (SPs) in doped graphene nanoribbon is proposed. The plasmons in THz region can be generated in a dopped graphene nanoribbon due to nonradiative excitation by emitters like two level quantum dots located along a graphene nanoribbon. The minimal population inversion per unit area, needed for the net amplification of SPs in a doped graphene nanoribbon is obtained. The dependence of the minimal population inversion on the surface plasmon wavevector, graphene nanoribbon width, doping and damping parameters necessary for the amplification of surface plasmons in the armchair graphene nanoribbon is studied. Besides, a new method for high-sensitivity plasmon spectroscopy is proposed based on the usage of a graphene spaser. The plasmon generation is suppressed and even break down near threshold due to absorption at the transition frequencies of the neighbouring nano-objects (molecules or clusters) under study. In result a dip in the spaser generation spectra appears. The sensitivity of this spaser spectroscopy near (slightly above) generation threshold can be very high. [Preview Abstract] |
Monday, March 3, 2014 3:42PM - 3:54PM |
D30.00007: Photocurrent Measurement of Multiple Top Gated Graphene Devices Trond Andersen, Qiong Ma, Nathaniel Gabor, Kenji Watanabe, Takashi Taniguchi, Pablo Jarillo-Herrero Inefficient electron-phonon relaxation in graphene results in long-lived hot carriers that proliferate over large spatial scales, associated with long-range energy and momentum transport. In order to investigate the propagation length of hot carriers, we report on photocurrent measurements using graphene devices with a global back-gate and multiple local top-gates. The purpose of the latter is to facilitate independent modulation of the Seebeck coefficient at different distances from the position of laser illumination. By varying the voltages of the top gates separately and measuring the change in photovoltage, we investigate the electronic temperature gradient at each gate through the Seebeck effect. [Preview Abstract] |
Monday, March 3, 2014 3:54PM - 4:06PM |
D30.00008: Scanning photocurrent microscopy of graphene subjected to a magnetic field Helin Cao, Grant Aivazian, Jason Ross, Sanfeng Wu, Pasqual Rivera, David Cobden, Xiaodong Xu The optoelectronic properties of graphene, converting light into photocurrent, are of great interest for both fundamental reasons and for device applications due to graphene's unique band structure and high carrier mobility. A photocurrent response has been observed in many previous measurements on a variety of graphene junction structures, such as single-to-bilayer junctions, p-n junctions, and graphene-metal junctions. Here we investigate the photocurrent response of graphene field-effect-transistor devices subjected to a perpendicular magnetic field. We will present scanning photocurrent microscopy results as a function of magnetic field and temperature, and discuss the underlying mechanisms. [Preview Abstract] |
Monday, March 3, 2014 4:06PM - 4:18PM |
D30.00009: Anisotropic photoinduced current injection in graphene Julien Rioux, John E. Sipe, Guido Burkard Quantum-mechanical interference effects are considered in carrier and charge current excitation in gapless semiconductors using coherent optical field components at frequencies $\omega$ and $2\omega$. Due to the absence of a bandgap, excitation scenarios outside of the typical operation regime are considered; we calculate the polarization and spectral dependence of these all-optical effects for single- and bilayer graphene. For linearly-polarized light and with one-photon absorption at $\omega$ interfering with $2\omega$ absorption and $\omega$ emission, the resulting current injection is five times stronger for perpendicular polarization axes compared to parallel polarization axes. This additional process results in an anisotropic current as a function of the angle between polarization axes, in stark contrast with the isotropic current resulting from the typical interference term in graphene [Rioux et al., PRB 83, 195406 (2011)]. Varying the Fermi level allows to tune the disparity parameter $d$ closer to typical values in GaAs [$|d|\approx 0.2$, Rioux and Sipe, Physica E 45, 1 (2012)]: from -1, when the additional process is fully Pauli-blocked, to -3/7, when it is fully accessible, thus facilitating polarization sensitive applications. [Preview Abstract] |
Monday, March 3, 2014 4:18PM - 4:30PM |
D30.00010: Investigating photoresponse in graphene by light polarization M. Eginligil, B.C. Cao, Z.L. Wang, C. Soci, T. Yu We report our photocurrent studies on single layer graphene (SLG), bilayer graphene (BLG) and trilayer graphene (TLG) by exciting with circularly polarized light. In addition to p-n junctions based on gated graphene field-effect-transistor (g-FET), it was recently demonstrated that in the graphene/metal interface large photocurrent (PC) can be generated and this PC can be manipulated by backgate voltage in a simple g-FET. In this work we fabricated g-FETs from mechanically exfoliated graphene and explored backgate voltage dependence of photon drag effect (PDE), linear and circular photogalvanic effect (CPGE) of SLG, BLG and TLG. In BLG, we noticed a cos$\theta $ dependence of the measured PC, where $\theta $ is the angle of incident light polarization, in addition to PDE and CPGE effects which have cos4$\theta $ and sin2$\theta $ dependence, respectively. This cos$\theta $ dependence is attributed to the Berry curvature related valley PC, which can be induced as a result of broken inversion symmetry and asymmetry in the two low energy valleys of BLG. The latter is absent in SLG and peculiar for ABA stacked TLG. By varying backgate voltage we distinguish all helicity dependent PC contributions. Our data show good agreement with the theory. [Preview Abstract] |
Monday, March 3, 2014 4:30PM - 4:42PM |
D30.00011: Highly sensitive hot electron bolometer based on disordered graphene Xiaosong Wu, Qi Han, Teng Gao, Rui Zhang, Yi Chen, Jianhui Chen, Gerui Liu, Yanfeng Zhang, Zhongfan Liu, Dapeng Yu A bolometer is a device that makes an electrical resistive response to the electromagnetic radiation resulted from a raise of temperature due to heating. The combination of the extremely weak electron-phonon interactions along with its small electron heat capacity makes graphene an ideal material for applications in ultra-fast and sensitive hot electron bolometer. However, a major issue is that the resistance of pristine graphene weakly depends on the electronic temperature. We propose using disordered graphene to obtain a strongly temperature dependent resistance. The measured electrical responsivity of the disordered graphene bolometer reaches $6\times10^6$ V/W at 1.5 K, corresponding to an optical responsivity of $1.6\times10^5$ V/W. The deduced electrical noise equivalent power is 1.2 fW/$\sqrt{\rm Hz}$, corresponding to the optical noise equivalent power of 44 fW/$\sqrt{\rm Hz}$. The minimal device structure and no requirement of high mobility for graphene make a step forward towards the applications of graphene hot electron bolometers. [Preview Abstract] |
Monday, March 3, 2014 4:42PM - 4:54PM |
D30.00012: Negative Photoconductivity and Carrier Heating in CVD Graphene James Heyman, Banteaymolu Alebachew, Andrew Banman, Zofia Kaminski, Rhyan Foo Kune, Jacob Stein, Aaron Massari, Jeremy Robinson Ultrafast photoexcitation of CVD graphene typically leads to a transient \textit{decrease} in conductivity. Previous reports identify two possible mechanisms for this decrease: carrier heating leading to a decrease in mobility, and a photo-induced population inversion producing a negative dynamic resistance. We present time-resolved THz transmission (TRTS) measurements which show that population inversion is not required to observe negative photoconductivity in CVD graphene and confirm the role of carrier heating. In $p$-type CVD graphene samples interband optical transitions are blocked for pump photon energies less than twice the Fermi energy. However, our pump photon-energy resolved TRTS measurements exhibit negative photoconductivity at all pump wavelengths investigated, indicating that interband excitation leading to population inversion is not required to observe this effect. In addition, we have performed TRTS measurements on CVD graphene in magnetic fields that separately probe carrier mobility and population. We find that negative photoconductivity following photoexcitation primarily arises from a decrease in carrier mobility, confirming the role of carrier heating. Research at NRL was supported by the Office of Naval Research. [Preview Abstract] |
Monday, March 3, 2014 4:54PM - 5:06PM |
D30.00013: Transport through Disordered Graphene Geometries in a Laser-Induced Floquet Topological State Arijit Kundu, Babak Seradjeh, Herbert Fertig Driving a system periodically can induce non-trivial topological properties. In graphene, for example, irradiation with circularly polarized laser can open up topological band-gaps. If current is injected from a lead with Fermi energy within that gap, for an open geometry electronic transport is mediated by topologically protected edge states. By contrast, in a periodic geometry (e.g., a nanotube), transport is dominated by evanescent modes below and above the gap. We study transport through these systems in the presence of disorder, which can result in remarkably large localization lengths and near-critical behavior with increasing disorder strength. [Preview Abstract] |
Monday, March 3, 2014 5:06PM - 5:18PM |
D30.00014: Growing up in the Spotlight: Optics of Graphene from Dot to Sheet Rico Pohle, Eleftheria Kavousanaki, Keshav Dani, Nic Shannon Graphene quantum dots have recently generated much interest due to their novel properties like the presence of zero-energy states, as well as their potential applications in quantum computing and bio-imaging. Here, we theoretically study triangular and hexagonal graphene quantum dots with zigzag and armchair edges within the tight binding model. We identify, and obtain the exact wave functions, for a class of highly degenerate electronic states with energy equal to the hopping parameter. We study the scaling of the degeneracy of these states versus dot size for the different types of dots, and understand their role in the optical absorption spectrum going from small quantum dots to the thermodynamic limit of an infinite graphene sheet. We investigate the role that these states play in connection to the excitons caused by the van Hove singularity in infinite graphene, and their influence on the nanoscale opto-electronic properties of graphene quantum dots. [Preview Abstract] |
Monday, March 3, 2014 5:18PM - 5:30PM |
D30.00015: Ghost Fano Resonance of Excitons in Twisted Bilayer Graphene Yufeng Liang Metallic systems are generally considered to be unable to harbor tightly bound excitons because of the strong screening effect as well as the absence of a finite band gap. Previously, exception has only been found in one-dimensional metallic carbon nanotubes due to the depressed screening effects and the symmetry gap. We explore the exciton spectra of twisted bilayer graphene (tBLG) and predict the existence of even more strongly bound exciton (with binding energy as large as ~0.5eV) in this system despite of its higher dimensionality. Based on our results from first-principles simulations and effective model calculations, a mechanism known as the ghost Fano resonance is proposed for the bound exciton formation in metallic systems beyond the dimensonality-related argument. Our results shed light on engineering the e-h excitations in the few-layer van der Waals heterojunction. [Preview Abstract] |
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