Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session D24: Focus Session: Nanotube manipulation and processing |
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Sponsoring Units: DMP Chair: Michael Mehl, Naval Research Laboratory Room: 326 |
Monday, March 16, 2009 2:30PM - 3:06PM |
D24.00001: Carbon nanotube devices: Sorting, Assembling, Characterizing Invited Speaker: Carbon nanotubes have been studied extensively over the last decade. Various exceptional properties have been revealed which still drive the vision about using carbon nanotube in future electronics, for instance as molecular nanoscale transistors or electromigration resistant interconnects. For many years a major obstacle was the inability to grow nanotubes with defined dimensions (length, diameter) and electronic properties (metallic,semiconducting). Recently those problems have been solved to a large extent by advanced sorting techniques. Today the challenge is to assemble nanotubes devices with defined properties to form a complex circuitry. As progress is made in making highly-integrated nanotube device arrays new characterization techniques have to be developed which allow testing large number of devices within an acceptable time. Along this line I will report on the state-of-the-art of sorting of carbon nanotube, as a base for nanotube device fabrication [1]. I will then explain our strategy to assemble high-density arrays of nanotube devices [2] and discuss a new characterization technique for nanotube devices [3]. Finally I will introduce a novel device engineering tool [4]. \\[4pt] [1] R. Krupke et al., ``Separation techniques for carbon nanotubes'' in Chemistry of Carbon Nanotubes, p.129-139, American Scientific Publishers 2008\\[0pt] [2] A. Vijayaraghavan et al., ``Ultra-Large-Scale Directed Assembly of Single-Walled Carbon Nanotube Devices'', Nano Lett. 7 (2007) 1556-1560\\[0pt] [3] A. Vijayaraghavan et al., ``Imaging Electronic Structure of Carbon Nanotubes by Voltage-Contrast Scanning Electron Microscopy'', Nano Resarch 1 (2008) 321-332\\[0pt] [4] C. W. Marquardt et al., ``Reversible metal-insulator transitions in metallic single-walled carbon nanotubes'', Nano Lett. 9 (2008) 2767-2772 [Preview Abstract] |
Monday, March 16, 2009 3:06PM - 3:18PM |
D24.00002: Self-healing and adsorbate-induced removal of defects on graphene and carbon nanotubes Leonidas Tsetseris, Sokrates Pantelides The presence of point defects is known to induce significant changes in the electronic, chemical, transport, and mechanical properties of graphitic systems. Here, we use first-principles calculations based on density-functional theory to describe several adatom-related processes that alter key physical traits of graphene and carbon nanotubes. We find that, while pairs of C adatoms and clusters of four or more self-interstitials stay idle unless the system is heated to very high temperatures, clustering of three C adatoms leads to removal of hillock-like features and creates mobile species, resulting in self-healing of defective structures. We also demonstrate the reactivity of defect pairs using hydrogen and oxygen as prototype adsorbates, and we show that interaction with extrinsic species is an alternative healing mechanism for adatom structures in the above systems. The results relate to the evolution of defects either during growth of carbon nanotubes or during post-growth treatment and operation of related devices. This work was supported in part by DOE Grant DEFG0203ER46096. [Preview Abstract] |
Monday, March 16, 2009 3:18PM - 3:30PM |
D24.00003: Self-similar mechanics of vertically aligned carbon nanotube organization Michael De Volder, Sameh Tawfick, Daniel Vidaud, A. John Hart It is well-known that carbon nanotube (CNT) growth from a dense arrangement of catalyst nanoparticles creates a self-organized vertically aligned CNT ``forest'' that offers attractive anisotropic mechanical, thermal, and electrical properties. Self-organization is governed by the CNT diameter and spacing, and the surface interactions between contacting CNTs. We demonstrate that arrays of CNT microstructures having micron-scale diameter organize in a similar manner as individual CNTs within a forest. For example, as postulated for CNT forests, entanglement of CNT microstructures during the initial stage of growth creates a self-supporting network, and this enables coordinated subsequent growth of the structures in the vertical direction. The alignment of these self-similar CNT forests is inversely related to the spacing of the microstructures, and like individual CNTs, widely-spaced microstructures that are not self-supporting fail to organize into an oriented superstructure. The growth rate and final forest height also depend on these geometric conditions, suggesting that mechanical interactions affect the collective progression and termination of a CNT film. This study and method offers new insights into the self-organization of one-dimensional nanostructures, and coordinated assembly of CNT microstructures offers opportunity for engineering energy-absorbing foams and photonic crystals. [Preview Abstract] |
Monday, March 16, 2009 3:30PM - 3:42PM |
D24.00004: Debundle of Single-Walled Carbon Nanotubes with Exfoliated Nanoplatelets Dazhi Sun, William Everett, Chien-Chia Chu, Hung-Jue Sue We report a simple and effective colloidal method to disperse single-walled carbon nanotubes (SWNTs) down to individual-tube level by utilizing exfoliated nanoplatelets in various solutions and polymer matrices. This approach yields a substantial amount of individual tubes without compromising their physical properties. The de-bundling and dispersion of SWNTs are confirmed by high-resolution transmission electron microscopy, UV-vis-NIR and Raman spectroscopy. After incorporated into polymers, SWNTs maintain individual dispersion. The dispersion mechanisms and implications of this approach are also discussed. [Preview Abstract] |
Monday, March 16, 2009 3:42PM - 3:54PM |
D24.00005: Motion and Manipulation of Suspended Single-Walled Carbon Nanotubes in Solution Ya-Qiong Xu, Arthur Barnard, Paul McEuen We have developed an optoelectronic imaging system which combines nanotube transistors with optical trapping techniques and the scanning photocurrent microscopy to investigate the motion of suspended single-walled carbon nanotubes in solution. This setup enables us to study the movement of nanotubes by monitoring their photocurrent images and to measure their thermal fluctuations through observing the movement of microbeads that are tightly attached to nanotubes by single-stranded DNA. By analyzing their thermal fluctuations, we are able to obtain the torsional and transversal stiffness of nanotubes and then calculate their diameters. We can also manipulate their motions by using an optical trap to pull on microbeads attached to nanotubes. [Preview Abstract] |
Monday, March 16, 2009 3:54PM - 4:06PM |
D24.00006: Processing of SWNT Dispersions -- Microfluidic Processing vs. Ultrasonication Tao Liu, Sida Luo, Chuck Zhang, Ben Wang Ultrasonication is the most commonly used processing technique for dispersing SWNTs in various media. High-power sonication enables the desired dispersability enhancement and the exfoliation of large SWNT bundles to smaller and even individual tubes. However, one disadvantage for this process is that the SWNT particles can be cut to shorter length. Using a newly developed characterization technique by us for quantifying the structures of SWNTs in a dispersion, we investigated the structural changes of SWNTs due to two different dispersion processing techniques, namely, microfluidic processing and ultrasonication. As a result, the microfluidic processing method shows significantly improved exfoliation efficiency as compared to ultrasonication. Moreover, the length of the exfoliated SWNT particles is maintained upon microfluidic processing, in contrast to the cutting effect caused by the high power sonication. In this presentation, we will discuss in-depth on the processing-structure-property relationships of SWNT dispersions processed by these two different processing methods. [Preview Abstract] |
Monday, March 16, 2009 4:06PM - 4:18PM |
D24.00007: Steric Mode Separation of Nanotubes Using Electric Field, Field-Flow Fractionation Frederick Phelan, Barry Bauer A Brownian dynamics simulation is used to study the separation of rodlike particles in Electric Field, Field-Flow Fractionation (EF-FFF), in which in addition to the FFF cross-flow, a uniform AC field acts in the gradient direction. Under these conditions, the electric field acts to align the tubes in the gradient direction in competition with both the shear field and Brownian motion. The simulation results show that as the rods become increasingly aligned, they undergo a transition from normal mode to steric mode separation. By exploiting field conditions in which either metallic or semi-conducting types are preferentially oriented relative to the other, this can be used in the context of nanotube separation as a means for separating tubes by type. [Preview Abstract] |
Monday, March 16, 2009 4:18PM - 4:30PM |
D24.00008: Thermal conductivity of vertically-aligned single-walled carbon nanotube film measured by 3$\omega$ method Kei Ishikawa, Saburo Tanaka, Koji Miyazaki, Junichiro Shiomi, Shigeo Maruyama Single-walled carbon nanotubes (SWNTs) have been expected to have extremely high thermal conductivity. However, the previously reported modeling and experimental works using individual SWNTs are too idealistic for the vertically-aligned single-walled carbon nanotube (VA-SWNT) film, in terms of defects, bundling effects, etc. In this work, we measured thermal conductivity of high purity VA-SWNT film synthesized by alcohol catalytic chemical vapor deposition (ACCVD) method [1]. We utilize thin film 3$\omega$ method for measuring thermal properties by depositing metal directly onto the VA- SWNT film. In the course of probing the intrinsic thermal conductivity, we discuss the effect of thermal boundary resistances at the nanotube-metal and nanotube-susbstrate boundaries. [1] Y. Murakami et al., Chem. Phys. Lett., 385 (2004), 298. [Preview Abstract] |
Monday, March 16, 2009 4:30PM - 4:42PM |
D24.00009: Optimal matching of thermal vibrations into carbon nanotubes K.G.S.H Gunawardana, Kieran Mullen Carbon nanotubes (CNTs) are promising candidates to improve the thermal conductivity of nano-composites. The main obstacle to these applications is the extremely high thermal boundary (Kapitza) resistance between the CNTs and their matrix. In this work our goal is to maximize the heat flux through the CNT by functionalizing their ends. We develop theoretical continuum models in which we vary the elasticity and density from surrounding medium to the CNT so as to maximize the transmission of thermal vibrations. We calculate the transmission coefficients using a scalar wave equation. Since the transport in CNT is strictly one dimensional, a Landauer formula is used to estimate the heat flux into the CNT. We determine the optimal continuous variation of elasticity and density with position for different geometries. We also investigate how to optimally match the nano-tubes to their matrix using a small number of discrete interfaces. Finally, we discuss the implications of these models for experiment. [Preview Abstract] |
Monday, March 16, 2009 4:42PM - 4:54PM |
D24.00010: Temperature dependence of the anharmonic decay of optical phonons in carbon nanotubes and graphite Ioannis Chatzakis, Hugen Yan, Daohua Song, Stephane Berciaud, Tony F. Heinz We report on the temperature dependence of the anharmonic decay rate of zone-center optical phonons in both single-walled carbon nanotubes and graphite from cryogenic temperatures to 650K. The measurements are performed using a pump-probe Raman scattering scheme with femtosecond (fs) laser pulses [Song et al. PRL 100,225503(2008)]. A nonequilibrium population of the zone-center (G-mode) optical phonons is created by an initial fs laser pulse. A subsequent fs probe pulse generates both Stokes and antiStokes Raman scattering, from which we infer the mode population of the G-mode phonons. We observe a large nonequilibrium phonon population in both systems, together with a room-temperature population lifetime of 1-2ps. The population decay is attributed to anharmonic coupling to lower-energy phonons [Bonini et al. PRL 99,176802(2007)]. We observe little T dependence of the decay rate below room temperature, but find a component growing roughly linearly with increasing T for $>$300K. We compare the behavior observed in nanotubes and graphite and discuss the implications of our results for the mechanism of the anharmonic decay of optical phonons in both systems. [Preview Abstract] |
Monday, March 16, 2009 4:54PM - 5:06PM |
D24.00011: Universal response of single-wall carbon nanotubes to radial compression: theory and experiment Helio Chacham, Ana Paula M. Barboza, Bernardo R. A. Neves Since the early 90's, the electronic and structural properties of single-wall carbon nanotubes (SWNTs) have been thoroughly investigated. Regarding SWNT mechanical properties, most of the attention has been given to their large resistance to axial tension, even though several electromechanical effects have been observed on radially compressed SWNTs, such as the predicted [1], and recently observed [2], metal-insulator transition. The present work brings a unifying picture to the process of radial compression/deformation of SWNTs, where experimental data are analyzed through a rescaling model yielding a universal-type behavior. Specifically, our AFM measurements show that the quantity $Fd^{3/2}(2R)^{-1/2}$, where $F$ is the force applied by the AFM tip (with radius $R$) and $d$ is the SWNT diameter, is a universal function of the compressive strain. Such universality is reproduced analytically in a model where the graphene bending modulus is the only fitting parameter. The application of the same model to the radial Young modulus $E_r$ leads to a further universal-type behavior that explains the large variations of the SWNTs $E_r$ reported in the literature. [1] M. S. C. Mazzoni and H. Chacham, Appl. Phys. Lett. 76, 1561 (2000). [2] A. P. M. Barboza et al., Phys. Rev. Lett. 100, 256804 (2008). [Preview Abstract] |
Monday, March 16, 2009 5:06PM - 5:18PM |
D24.00012: Carbon Nanomaterials Under Highly Energetic Heavy Ion Irradiation J.M. Callahan, B.W. Jacobs, K. McElroy, M.A. Crimp, R.M. Ronningen, A.F. Zeller, H.C. Shaw The radiation performance of carbon nanomaterials: carbon onions and single-walled carbon nanotubes under highly energetic heavy ion irradiation was investigated, with highly oriented pyrolytic graphite (HOPG) used as the control. Samples were irradiated with a krypton-86 beam at 142 MeV/nucleon, a krypton-78 beam at 140 MeV/nucleon, and a calcium-48 beam at 140 MeV/nucleon and 70 MeV/nucleon at the National Superconducting Cyclotron Laboratory at Michigan State University. Fundamental structural and chemical modifications were investigated using Micro Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). Results indicated that the radiation resiliency of the single-walled carbon nanotubes exceeded that of highly oriented pyrolytic graphite, while the carbon onions showed structural modifications of the outer onion layers in the form of faceting and onion fusion. [Preview Abstract] |
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