Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session W44: Graphene and Carbon Nanotubes: Functionalization and Sensing Applications |
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Sponsoring Units: DCMP Chair: Enrique Cobas, Naval Research Laboratory Room: Mile High Ballroom 4C |
Thursday, March 6, 2014 2:30PM - 2:42PM |
W44.00001: Fabrication and Investigation of resonance frequency sensitive Graphene/ZnO based gas sensor in room temperature Mehdi Namazi, Seyyed Mohsen Jebreiil Khadem, Yaser Abdi, Sara Darbari, Fatemeh Ostovari Graphene/ZnO hybrid was used to fabricate a highly selective and sensitive gas sensor. ZnO nanowires in the structure have three important roles: reduction of grapheme oxide to obtain graphene, acting as sensing element and mechanical actuation using their piezoelectric properties. A selected set of chemicals vapors was tested on the fabricated sensor. We have found that chemical vapors change the resonance frequency of the graphene/ZnO in addition to the electrical resistivity of the structure. Variation of the mechanical and electrical characteristics of the graphene/ZnO due to gas exposure make the graphene/ZnO based sensors highly selective and reliable device for gas sensing with distinctive signatures for specific gases. We have introduced an alternative frequency modulation gas detection method here in which the gas absorption on the graphene/ZnO can affects resonance frequency of the ZnO nanowires. Such alternative method can be utilized for detection of absorbed gases which do not change the resistivity of the sensing element significantly. Also the sensitivity of the graphene/ZnO based gas sensor was investigated under mechanical actuation. [Preview Abstract] |
Thursday, March 6, 2014 2:42PM - 2:54PM |
W44.00002: Gase sensing using on terahertz emissions from graphene-coated InP surfaces Tonouchi Masayoshi, Iwao Kawayama, Yuki Sano, Khandoker Salek, Hironaru Murakami, Mika Tabata, Minjie Wang, Junichiro Kono, Robert Vajtai, Pulickel Ajayan Electrical and optical properties of graphene are known to be affected by the adsorption of gas molecules, which can be used for developing a highly sensitive gas sensor. In this study, we demonstrate a new approach for environmental gas sensing using terahertz emission from graphene-coated semiconductor wafers. Specifically, we show that the waveforms of terahertz radiation from graphene-coated InP sensitively change with the type of the atmospheric gas and the laser illumination time. The change of the terahertz waveforms in different environmental gases can be explained by modification of the surface depletion-layer potential of InP due to the surface dipole induced by the adsorbed gas molecules. Moreover, additional UV light illumination enhances the change of terahertz waveforms in oxygen, apparently due to photo-oxidation of graphene. We have developed a theoretical model that can explain these experimental observations in a semi-quantitative manner. [Preview Abstract] |
Thursday, March 6, 2014 2:54PM - 3:06PM |
W44.00003: Detection of the first order phase transition in water with carbon nanotube layer Vladimir Samuilov, Nikolay Poklonski We have developed a new generation of the icing conditions sensors. These sensors are based on the detection of a molecular thin layer of absorbed water molecules, transforming into ice by detection of nonmonotonic variation of the resistance of the carbon nanotube sensor. Carbon nanotube layers could be utilized as an inexpensive and effective sensors of humidity and icing conditions, suitable for applications in aviation and different industries. [Preview Abstract] |
Thursday, March 6, 2014 3:06PM - 3:18PM |
W44.00004: Transport of nanoparticles in porous media with Dissipative Particle Dynamics (DPD) simulation Minh Vo, Dimitrios Papavassiliou Nanoparticles can serve as nanosensor devices in oil recovery processes, because of their ability to propagate in porous media. We employ DPD simulations to explore the factors affecting the retention and mobility of carbon nanotubes (CNT) in porous media. Compared to molecular dynamics simulations, longer time and length scales can be obtained with DPD, while the hydrodynamic properties of system are also maintained. Besides, complex flow structures can be handled by DPD in a simple manner (using frozen DPD beads for solid surface). In our calculations, packed-sphere geometry is utilized to create porous media. After equilibrium, CNTs are released into the flow. The interaction between the CNTs and the solid surface is considered by applying both shifted force Lenard-Jones and Morse potential in the DPD model. Different sizes of CNTs are investigated, in order to study the effect of the aspect ratio on the hydrodynamic forces as well as the rotation of CNTs while moving with the flow. In addition, the mobility of CNTs is discussed by computing their trajectory in the flow and comparing the cylindrical particles to spherical. [Preview Abstract] |
Thursday, March 6, 2014 3:18PM - 3:30PM |
W44.00005: Using graphene to track the conductivity of C$_{60}$ Claudia Ojeda-Aristizabal, Seita Onishi, Haider Rasool, Celeste Carruth, Alex Zettl C$_{60}$ exhibits superconductivity when intercalated with alkali metals [1,2]. This intercalation originates charge doping as well as a modification of the lattice constant, giving rise to an increased density of states at the Fermi energy of C$_{60}$. Here we study the change of the electronic transport in C$_{60}$ by charge doping alone. We deposit C$_{60}$ on a graphene device that has two metallic electrodes and a back gate. By measuring the conductance of graphene, we track any changes in the conductance of C$_{60}$, connected in parallel to graphene. We will show preliminary transport data that demonstrates charge transfer into C$_{60}$. \\[4pt] [1] A. F. Hebard, M.J. Rosseinsky, R. C. Haddon, D. W. Murphy, S. H. Glarum, T.T. M. Palstra, A. P. Ramirez and A. R. Kortan. Nature 350, 600 (1991).\\[0pt] [2] R. M. Fleming, A.P. Ramirez, M.J. Rosseinsky, D. W. Murphy, R.C. Haddon, S. M. Zahurak and A. V. Makhija. Nature 352, 787 (1991). [Preview Abstract] |
Thursday, March 6, 2014 3:30PM - 3:42PM |
W44.00006: First-principles study of multi-control doping using azobenzene adsorbed on graphene Jonathan Trinastic, Hai-Ping Cheng The high carrier mobility in graphene promises its utility in electronics applications, however more research is necessary to find optimal doping methods. Azobenzene (AB) is a widely used organic molecule for switchable optoelectronic devices that can be synthesized with a wide variety of ligands and deposited on graphene. Using first-principles calculations, we investigate the doping of graphene by physisorbed azobenzene molecules with various electron-donating and --accepting ligands. We confirm previous experimental results (Peimyoo et al 2011, \textit{ACS Nano},6(10),8878) that demonstrate greater p-doping of graphene for the \textit{trans }compared to \textit{cis }configuration when using a SO$_{\mathrm{3}}$ electron-accepting ligand, and we find different levels of p-doping when using other ligands. We extend these findings by examining the doping effects of an applied electric field and applied strain to the graphene, which leads to changes in doping for both the \textit{trans }and \textit{cis} isomers. These findings demonstrate a new type of multi-switch device combining light, electric field, and strain to change carrier concentration in graphene. [Preview Abstract] |
Thursday, March 6, 2014 3:42PM - 3:54PM |
W44.00007: Graphene- and graphene oxide- based multisensor arrays for selective gas analysis Alexey Lipatov, Alexey Varezhnikov, Victor Sysoev, Andrei Kolmakov, Alexander Sinitskii Arrays of nearly identical graphene devices on Si/SiO$_{2}$ exhibit a substantial device-to-device variation, even in case of a high-quality chemical vapor deposition (CVD) or mechanically exfoliated graphene. We propose that such device-to-device variation could provide a platform for highly selective multisensor electronic olfactory systems. We fabricated a multielectode array of CVD graphene devices on a Si/SiO$_{2}$ substrate, and demonstrated that the diversity of these devices is sufficient to reliably discriminate different short-chain alcohols: methanol, ethanol and isopropanol. The diversity of graphene devices on Si/SiO$_{2}$ could possibly be used to construct multisensor systems trained to recognize other analytes as well. Similar multisensory arrays based on graphene oxide (GO) devices are also capable of discriminating these short-chain alcohols. We will discuss the possibility of chemical modification of GO for further increase the selectivity of GO multisensory arrays. [Preview Abstract] |
Thursday, March 6, 2014 3:54PM - 4:06PM |
W44.00008: Gas sensing of a saturated tin/defective graphene device Sherif Tawfik, X. Cui, Damien Carter, S. Ringer, C. Stampfl The sensitivity and selectivity of defective graphene to gases is enhanced by implanting single metal adatoms into vacancy sites. Knowledge of the behavior of these devices under the incremental adsorption of gas molecules until saturation is essential for determining the sensitivity of the device in realistic situations as well as for evaluating the applicability of the device in molecular capture and storage. We present a DFT study of incremental gas adsorption of CO$_{2}$, NO$_{2}$, SO$_{2}$ and H$_{2}$S gases on tin adatom-double vacancy graphene system, in the presence and absence of O$_{2}$. Within the NEGF formalism, we analyze the sensitivity and selectivity of the saturated device to the gas species, showing distinctive transport features for each of the gas species. [Preview Abstract] |
Thursday, March 6, 2014 4:06PM - 4:18PM |
W44.00009: Electronic transport properties of graphene with 5 \textit{d} metal adatoms Yilin Wang, Shudong Xiao, Wenzhong Bao, Janice Reutt-Robey, Michael Fuhrer Electronic transport properties of graphene are highly sensitive to adsorbates on its surface. Adsorbates can affect graphene through doping and scattering, and 5$d$ metal adsorbates have been predicted to induce strong spin-orbit coupling and open a bandgap [1]. Here we study the\textit{ in-situ} transport properties of single-layer graphene doped with 5$d$ heavy metal atoms. Iridium was deposited on graphene at a substrate temperature of 7 K under ultra-high vacuum condition. Gate-dependent conductivity measurements show that the mobility and minimum conductivity of graphene decrease with increasing Iridium concentration. The results are in agreement with the self-consistent theory of graphene with random charged impurities [2], and do not indicate any significant bandgap in graphene with Iridium adatoms. We will also discuss temperature-dependent measurements, and co-adsorption of Iridium and krypton.\\[4pt] [1] Phys. Rev. Lett. \textbf{109}, 266801 (2012)\\[0pt] [2] \textit{PNAS} \textbf{104}, 18392 (2007) [Preview Abstract] |
Thursday, March 6, 2014 4:18PM - 4:30PM |
W44.00010: Rigid band shifts, charge pinning, and charge transport through graphene junctions with wetting metal contacts Tobias Bothwell, Salvador Barraza-Lopez It is a common perception that graphene band shifts cannot be determined directly when attached to chemisorbed (``wetting'') metals due to the hybridization of graphene bands around the Dirac point. Graphene has deeper energy (sigma) bands which don't hybridize with the metal's bands, providing a definite measure of actual shifts. Looking at hybridization in a controlled way (by varying the metal/graphene separation by hand) one realizes the shifts can actually be considered rigid, i.e., $\sigma -$ and $p-$ bands shift by about the same energy $\Delta_{\mathrm{E}}$. In a related context, charge depinning is the modification of graphene's electron density at a metal/graphene interface with a (back) gate. Depinning happens at metal/graphene interfaces with physisorbed (non-wetting) metals. Oxidation or contamination at the interface can lead to charge depinning as well. Using first-principles calculations, we establish a link between charge depinning at a wetting metal/graphene interface and the quality of such an interface. For this purpose, metal/graphene/insulator structures are studied under transverse bias. We also report transmission coefficients through nanoscale two-terminal graphene/metal junctions. [Preview Abstract] |
Thursday, March 6, 2014 4:30PM - 4:42PM |
W44.00011: Controlling the electronic structure of graphene using surface-adsorbate interactions Piotr Matyba, Adra Carr, Cong Chen, Margaret M. Murnane, Henry C. Kapteyn, David L. Miller, Mark W. Keller, Guowen Peng, Manos Mavrikakis, Stefan Mathias Strong coupling with the substrate, i.e. C-Ni hybridization, causes that the $\pi $ state maximum in graphene on Ni(111) is shifted to below the Fermi level, resulting in a band gap of 2.8 eV.[1, 2] The intercalation of noble metals to underneath graphene can reduce this band gap by decoupling graphene from the substrate.[3] Here we use angle-resolved x-ray photoemission spectroscopy and DFT calculations to explore the influence of Na adsorbate on the electronic structure of graphene on Ni(111).[1] We show that the carefully controlled electronic surface-adsorbate interactions reduce the band gap to 1.3 eV with no need of intercalation, since the strong graphene-substrate coupling is counterbalanced by the coupling to the adsorbate. Subsequent intercalation drastically changes the electronic structure, reducing the band gap to \textless 180 meV, and decoupling graphene from the substrate. Our results demonstrate full band gap closing using an adsorbate for the first time, and suggest that surface-adsorbate interactions make it possible to control the band gap, either statically or dynamically, which is potentially useful for novel electronics. [1] P. Matyba et al., in submission (2013), [2] A. Gruneis et al., Physical Review B 77 (2008), [3] A. Varykhalov et al., Physical Review B 82 (2010). [Preview Abstract] |
Thursday, March 6, 2014 4:42PM - 4:54PM |
W44.00012: Improving the electrical characteristics of graphene field effect transistors by hexamethyldisilazane interaction Sk. Chowdhury, Somayyeh Rahimi, Sushant Sonde, Li Tao, Sanjay Banerjee, Deji Akinwande We report the improvement of the electrical characteristics of graphene field effect transistors (FET) by hexamethyldisilazane (HMDS) passivation. Sample is left in liquid HMDS after complete back gated FET fabrication. Both electron and hole field effect mobilities are improved by 1.5X - 2X, accompanied by effective residual carrier concentration reduction. Dirac voltage also moves closer to zero. Various techniques for HMDS application are investigated. Time evolution of mobility data shows that mobility improvement saturates after a few hours of HMDS dosing. Temperature-dependent transport measurements show small mobility variation between 77K and room temperature (295K) before HMDS application. But mobility at 77K is almost 2 times higher than mobility at 295K after HMDS application. The best CVD devices achieve a mobility of $\sim$ 20,000 cm2/V-s at 77K. Performance improvement is observed for FETs made with exfoliated graphene and for FETs made on hydrophobic substrate- an HMDS-graphene-HMDS sandwich structure. Raman spectroscopic analysis shows that G peak width is increased, G peak position is down shifted and intensity ratios between 2D and G peak is increased after HMDS application. AFM data shows increased RMS roughness after HMDS application. [Preview Abstract] |
Thursday, March 6, 2014 4:54PM - 5:06PM |
W44.00013: The range of two-body adsorbate-adsorbate interactions on the surface of graphene Dmitry Solenov, Chad Junkermeier, Thomas L. Reinecke, Kirill A. Velizhanin Tunable functionalization of ``all-surface'' materials is a promising area of fundamental and applied research. Two-body interactions between adsorbed atoms or molecules on surfaces, such as graphene, are crucial to a variety of applications, ranging from transport to photovoltaics and DNA manipulations. We present our recent results for adsorbate-adsorbate interactions between mono-valent and between bi-valent adsorbates on graphene. These interactions are dominated by direct Coulomb coupling and exchange of itinerant electrons. A model Hamiltonian that encompasses different types of adsorbates is constructed and parameterized from ab initio density functional theory. The range of interactions is found to depend strongly on the local adsorbate-substrate bonding mechanism and on the chemical potential. [Preview Abstract] |
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