Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session W45: Graphene: Functional Interfaces |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Yufeng Hao, University of Texas at Austin Room: Mile High Ballroom 4D |
Thursday, March 6, 2014 2:30PM - 2:42PM |
W45.00001: Giant Current-Perpendicular-to-Plane Magnetoresistance in Multilayer-Graphene Grown on Nickel Srikrishna Bodepudi, Abhay Singh, Sandipan Pramanik Magnetoresistance (MR), the change in electrical resistance as a function of an external magnetic field, is a key effect in magnetic field sensors. Ferromagnet-nonmagnet multilayers which often exhibit giant magnetoresistance or tunnel magnetoresistance effects are traditionally used to realize magnetic field sensors. MR in graphitic systems has drawn significant attention in recent years due to the unique crystal structures of these materials. In this work we explore another class of layered structure in which multilayer graphene (MLG) is as-grown on nickel substrate by chemical vapor deposition (CVD). We observed a large negative current-perpendicular-to-plane (CPP) MR (\textgreater 10$^{4}$ {\%}) in this system when the magnetic field is normal to the plane. The observed effect can be qualitatively explained within the framework of interlayer MR. Graphene layers in CVD-grown MLG are generally weakly coupled, which can be viewed as a stack of two dimensional Dirac electron system. A large negative interlayer MR can be expected in CPP geometry when the charge transport occurs between the zero mode Landau levels of weakly coupled Dirac electron system. This effect is stronger when the magnetic field is normal to the plane. We also showed that the defect free graphene is essential in addition to the weakly coupled graphene layers to observe the large negative MR. Due to large MR value and its persistence at room temperature, this effect is expected to have commercial implications and encourage further research on MLG physics. [Preview Abstract] |
Thursday, March 6, 2014 2:42PM - 2:54PM |
W45.00002: Fabrication and transport studies of graphene-superconductor heterostructures Jiuning Hu, Tailung Wu, Jifa Tian, Yong Chen Recently, graphene based stacked heterostructures, e.g., graphene and boron nitride (BN) multi-layers, have attracted much attention as a system to study novel interaction-driven physics (e.g., excitonic condensation) and perform interesting measurements (eg. Coulomb drag and tunneling). The realm of graphene-superconductor heterostructures remains less unexplored, while such a system offers various interesting prospects (effects of superconductor vortices lattices on over-layering graphene and quantum Hall states, where novel phenomena such as anionic excitations have been predicted). We have used polyvinyl alcohol (PVA) based carrier films and a micro-manipulator to transfer mechanically exfoliated flakes and fabricated graphene/BN/NbSe$_2$ structures to study the transport properties of graphene in close proximity to electrically isolated superconducting NbSe$_2$ films. The NbSe$_2$ film shows the superconducting transition temperature of $\sim$7 K and upper critical field of $\sim$3.5 T after device fabrication. We will present results from magneto-transport in graphene and graphene-NbSe$_2$ Coulomb drag and tunneling measurements. [Preview Abstract] |
Thursday, March 6, 2014 2:54PM - 3:06PM |
W45.00003: Two dimensional epitaxial graphene - SiC/SiO$_x$ field effect transistors Jan Kunc, Yike Hu, James Palmer, Zelei Guo, Claire Berger, Walter de Heer We have produced and measured two dimensional (2D) field effect transistors composed of graphene source and drain and a 2D SiC/SiO$_x$ channel supplied with a top gate. The devices have been measured in a wide range of gate voltages and temperatures. Careful attention was focused on the SiC/SiO$_x$ channel formation and graphitization conditions. The channel was characterized by XPS, LEED, atomic and electrostatic force microscopy and Raman spectroscopy. On to off current ratios up to 10$^6$ have been achieved and sub-threshold swings up to 200 mV/decade have been attained with on-state currents in the sub-miliamp range. The channel formation as well as graphene/SiC junction including charge transfer in the graphene are modeled solving the coupled Poisson equation and Schr\"{o}dinger equation in the effective mass approximation. The standard models of Metal Induced Gap States (MIGS) and Charge Neutrality Level concepts successfully reproduce the experimental data. The combined contributions of the space charge limited current in the channel and back-to-back Schottky diodes at the channel junctions are discussed. The thermionic and tunneling nature of the barriers is analyzed in these quasi two dimensional devices. [Preview Abstract] |
Thursday, March 6, 2014 3:06PM - 3:18PM |
W45.00004: Measuring Schottky barrier height at graphene/SiC junction D. Tomer, L. Hudy, S. Rajput, L. Li When graphene is interfaced with a semiconductor, a Schottky junction forms with rectifying properties. In this work, we measured the Schottky barrier heights of graphene/SiC Schottky diodes using current-voltage (I-V) measurement. Chemical vapor deposited graphene was transferred onto semiconductor surfaces of opposite polarization: the hydrogen-terminated Si- and C-faces of $\alpha $-SiC, which was confirmed by Raman spectroscopy and scanning tunneling microscopy. The Schottky barrier height is found to be sensitive to the polarization of the substrate and surface preparation. On the Si-face, a barrier of 0.47 eV is found. These results will be compared with earlier work as well as our \textit{in situ} scanning tunneling spectroscopy results [1]. [1] Rajput et al., Nature Comm. (DOI: 10.1038/ncomms3752). [Preview Abstract] |
Thursday, March 6, 2014 3:18PM - 3:30PM |
W45.00005: Quasiparticle carrier dynamics in graphene from first principles Cheol-Hwan Park, Nicola Bonini, Thibault Sohier, Georgy Samsonidze, Boris Kozinsky, Matteo Calandra, Francesco Mauri, Nicola Marzari It is important to understand how a charge carrier in real materials interacts with other charge carriers or with the lattice vibration; these two effects, electron-electron interactions and electron-phonon interactions, respectively, largely determine the quasiparticle and transport properties of a material. In this presentation, we will show that some aspects of quasiparticle dynamics in graphene can be described by first-principles calculations considering these two effects. [Preview Abstract] |
Thursday, March 6, 2014 3:30PM - 3:42PM |
W45.00006: ABSTRACT WITHDRAWN |
Thursday, March 6, 2014 3:42PM - 3:54PM |
W45.00007: Electron-electron interaction effects in monolayer graphene Edwin Barnes Electron-electron interactions are expected to play an important role in graphene due to the absence of screening near the charge neutrality point, potentially leading to strong deviations from the Fermi liquid description. While such deviations have yet to be observed, there is experimental evidence of significant Dirac cone squeezing, a phenomenon which is consistent with renormalization of the Fermi velocity due to interaction effects. We show that while a first-order renormalization group analysis gives qualitative agreement with experimental observations of graphene both on substrates and in vacuum, a second-order analysis reveals an interacting critical point in suspended graphene, signifying either a quantum phase transition or a breakdown of the renormalization group approach. [Preview Abstract] |
Thursday, March 6, 2014 3:54PM - 4:06PM |
W45.00008: Growth of graphene on sapphire by molecular beam epitaxy Sheng Wang, Lara Fernandes dos Santos, Ulrich Wurstbauer, Lei Wang, Loren N. Pfeiffer, James Hone, Jorge M. Garcia, Aron Pinczuk Graphene growth by direct deposition of carbon atoms on dielectric substrates in a MBE environment has potential for large area fabrication of graphene layers. We explore the optimal graphene growth on sapphire c-plane surface with gradients of carbon flux and substrate temperature. Single- and bi-layer nanocrystalline graphene with sharp Raman bands are achieved at temperature around 1200 C. Atomic force microscopy (AFM) images uncover the presence of etch pits which suggest a carbon removal mechanism known as ``carbo-thermal reduction''. The average spacing between etch pits (of about 100 nm) defines an upper limit of nanocrystal size. Tuning the easily controlled incident carbon flux and the markedly temperature dependent carbo-thermal reduction of sapphire should enable the growth of high quality graphene layers on large area sapphire substrates. [Preview Abstract] |
Thursday, March 6, 2014 4:06PM - 4:18PM |
W45.00009: Piezoelectric surface acoustical phonon limited mobility of electrons in graphene on a GaAs substrate Samvel Badalyan, Shuhui Zhang, Wen Xu, Francois Peeters We study the mobility of Dirac fermions in monolayer graphene on a GaAs substrate, limited by the combined action of the extrinsic potential of piezoelectric surface acoustical phonons of GaAs (PA) and of the intrinsic deformation potential of acoustical phonons in graphene (DA). In the high temperature ($T$) regime the momentum relaxation rate exhibits the same linear dependence on $T$ but different dependences on the carrier density $n$, corresponding to the mobility $\mu\propto 1/\sqrt{n}$ and $1/n$, respectively for the PA and DA scattering mechanisms. In the low $T$ Bloch-Grueneisen regime, the mobility shows the same square-root density dependence, $\mu\propto \sqrt{n}$, but different temperature dependences, $\mu\propto T^{-3}$ and $ T^{-4}$, respectively for PA and DA phonon scattering. [Preview Abstract] |
Thursday, March 6, 2014 4:18PM - 4:30PM |
W45.00010: Magneto-optical properties of graphene on polar substrates Benedikt Scharf, Vasili Perebeinos, Jaroslav Fabian, Igor \v{Z}uti\'c We theoretically study the effect of polar substrates on the magneto-optical conductivity of doped monolayer graphene, where we particularly focus on the role played by surface polar phonons (SPPs). Our calculations suggest that polaronic shifts of the intra- and interband absorption peaks and the loss of spectral weight at these peaks due to electron-SPP scattering can be significantly larger for polar substrates than in graphene on nonpolar substrates, where only intrinsic graphene optical phonons with much higher energies contribute. These effects can be strongly temperature dependent, most noticeably in polar substrates with small SPP energies such as HfO$_2$. [Preview Abstract] |
Thursday, March 6, 2014 4:30PM - 4:42PM |
W45.00011: Characteristic of graphene field effect transistor with ferroelectric gate dielectric Somyeong Shin, Hyewon Du, Taekwang Kim, Jong-Hyuk Yoon, Eun-Kyu Lee, Seungmin Cho, Sunae Seo The increase of charge carrier concentration along with the mobility is essential to improve the conductance graphene. The replacement of high dielectric constant (high-k) materials provides this but in graphene charge carrier density could be limited by quantum capacitance of graphene with high-k gate dielectric. Y2O3 was one of materials intensively studied. Ferroelectric materials could also provide the other functionality using nonvolatile characteristic of remanent polarization as well as high charge carrier density. Several researches were reported for nonvolatile memory device combined with graphene and ferroelectric. everal previous experimental data seems to show the entangled hysteresis due to ferroelectric polarization and uncontrolled external impurity external charge in the electrical property and significant influences of interface states in ferroelectric and graphene interface.. In this study, we attempt to comprehend complicated hysteresis and the influence of charge carrier concentration by quantum capacitance and interface states qualitatively. We fabricated graphene ferroelectric field-effect transistor (GFFET) with PtZr$_{\mathrm{x}}$Ti$_{\mathrm{1-x}}$O$_{3}$(PZT) as gate dielectric and studied the effect on the transport property of electron or hoe conduction by interface states and ferroelectric polarization using gate voltage dependent capacitance and current --voltage experimental data at different temperature. [Preview Abstract] |
Thursday, March 6, 2014 4:42PM - 4:54PM |
W45.00012: Ferroelectric Superlattices as a route to clean Graphene-ferroelectric Interfaces Mohammed Yusuf, Matthew Dawber, Xu Du A good interface between ferroelectric surfaces and graphene sheets can enable a new generation of multifunctional devices in which the ferroelectric material is used to control the properties of graphene. Ferroelectric superlattices, in particular PbTiO$_{3}$/SrTiO$_{3}$ (PTO/STO), provide us with a unique opportunity for studying the graphene-ferroelectric interface. The ferroelectric-paraelectric transition temperature of the superlattices is tunable by varying the PTO volume fraction. Using devices with different PTO volume fractions and different ferroelectric strength, we have successfully demonstrated ferroelectric hysteresis, charge-trapping associated anti-hysteresis, and cross-over from anti-hysteresis to hysteresis over a wide temperature range from 300K down to 4K. These results allow us to establish a deeper understanding of the graphene-ferroelectric interface. Contrary to the common understandings that the charge trapping centers and anti-hysteresis originate mainly from contaminants and adsorbates trapped between graphene and ferroelectric substrates during fabrication, we found that significant contribution of charge trapping may come from defects in the ferroelectric substrate itself, and we explore approaches to eliminating these. [Preview Abstract] |
Thursday, March 6, 2014 4:54PM - 5:06PM |
W45.00013: Characterization of plasmon propagation in graphene on PZT substrates via infrared nano-imaging M.D. Goldflam, Guangxin Ni, Zhe Fei, A.S. McLeod, Barbaros Ozyilmaz, Antonio Castro Neto, Michael Fogler, D.N. Basov Using scattering-type scanning near-field optical microscopy, we have characterized graphene plasmons on a graphene-lead zirconate titanate (PZT) back-gated structure. By applying modest back-gate voltages of $\pm$1 V across the PZT, we have been able to induce variations in the graphene plasmon wavelength of more than $\sim$200 nm. The change in plasmon wavelength we observe corresponds to a shift in carrier concentration in the graphene by more than one order of magnitude. Additionally, we describe the plasmonic losses originating from the presence of PZT in such a device. Our results also suggest that persistent tuning of the graphene plasmon may be achieved by utilizing the ferroelectric nature of PZT. [Preview Abstract] |
Thursday, March 6, 2014 5:06PM - 5:18PM |
W45.00014: Effect of Remote Surface Optical Phonon Scattering in Graphene Gated by Single Crystal Ferroelectric Oxide Thin Films Zhiyong Xiao, Anil Rajapitamahuni, Stefan Schoeche, Jason Hoffman, Charles Ahn, Mathias Schubert, Xia Hong We have studied the effect of remote surface optical (RSO) phonon on the carrier mobility in graphene gated by a ferroelectric Ba$_{0.6}$Sr$_{0.4}$TiO$_{3}$ (BSTO) substrate. Single crystal 100-400nm BSTO films are grown epitaxially on Nb doped SrTiO$_{3}$ substrates. Graphene flakes are mechanically exfoliated onto BSTO and single and bi-layer flakes are fabricated into field effect devices via e-beam lithography. All samples exhibit resistivity hysteresis induced by ferroelectric switching at low temperature, which can be used for nonvolatile memory operations. Single layer graphene exhibits high mobility with $\mu_{Hall}$ $\sim$ 10,000 cm$^{2}$/Vs at carrier density of 3.5x10$^{12}$ cm$^{-2}$ at 10K. Above 80K, We observe a sharp rise in resistivity as a function of temperature $\rho $(T), which is attributed to the RSO phonon scattering form the BSTO gate. We have extracted the dominant RSO phonon mode from $\rho $(T) and compared it with results extracted from independent spectroscopic ellipsometry measurements. We will also discuss the temperature dependence of resistivity in bi-layer graphene gated by BSTO. [Preview Abstract] |
Thursday, March 6, 2014 5:18PM - 5:30PM |
W45.00015: Electrical quality improvement of thin Y$_{2}$O$_{3}$ topgates in graphene FETs by high-pressure O$_{2}$ post-deposition annealing Kosuke Nagashio, Kaoru Kanayama, Tomonori Nishimura, Akira Toriumi Although extensive research effort has focused on equivalent oxide thickness scaling by the deposition of ultrathin high-$k$ dielectrics on graphene, these dielectrics still suffer from leakage currents under high electric fields. This leakage is a critical concern for the increase in the on-current. Here, we demonstrate a considerable suppression of the gate leakage current by using Y$_{2}$O$_{3}$ film annealed in high-pressure O$_{2}$ at 100 atm (HP-PDA) in top-gated graphene FETs. Consequently, the quantum capacitance measurement for the monolayer graphene reveals the highest Fermi energy modulation ($E_{\mathrm{F}} =$ $\sim $0.52 eV, i.e., the carrier density of $\sim $2 $\times$ 10$^{13}$ cm$^{-2})$ in the solid-state topgate insulators reported so far. HP-PDA of Y$_{2}$O$_{3}$ enables to realize the robust and reproducible top-gated graphene FETs. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700