Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session Q36: Carbon Nanotubes and Other Nanostructured Materials: Sensing, Transport, and Optical Properties |
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Sponsoring Units: DCMP Chair: Zhigang Jiang, Georgia Tech Room: 408 |
Wednesday, March 18, 2009 11:15AM - 11:27AM |
Q36.00001: Effect of Localized Covalently Attached Oxygen Functionalization on the Transport Properties of Metallic Carbon Nanotubes Md. Ashraf, Nicolas Bruque, Rajeev Pandey, Philip Collins, Roger Lake We perform of a comprehensive study of the effect of covalent oxygen attachment on the transmission of metallic carbon nanotubes (CNTs). Oxygen attachment on the CNT surface favors an ether type bond. Two oxygen atoms attached on the CNT surface within the same carbon ring on parallel bonds are energetically the most stable attachment configuration. In an armchair CNT, oxygen attachment favors the C-C bonds orthogonal to the CNT axis. Correlated addition propagates axially along parallel orthogonal bonds. In a zigzag CNT, oxygen attachment prefers the slanted bond, and correlated addition propagates spirally along parallel slanted bonds. Closely spaced oxygen attachment on the armchair and zigzag CNT surfaces causes a dip in transmission symmetrically away from the Fermi level. A clustered group of oxygen atoms covalently attached to a single-walled metallic zigzag CNT can result in a one order of magnitude drop in transmission that is asymmetric with respect to the Fermi energy resulting in a qualitative resemblance to conductance versus gate voltage curves observed experimentally [Science 315, 77 (2007)]. Calculations use density functional theory combined with non-equilibrium Green functions. [Preview Abstract] |
Wednesday, March 18, 2009 11:27AM - 11:39AM |
Q36.00002: Molecular Modifications of the Electronic Characteristics of Carbon Nanotube Field-Effect Transistors Kan-Sheng Chen, P. Xiong, S.A. McGill We report a systematic examination of the effects of an organic self-assembled monolayer at the electrode/nanotube interface on the key electrical properties, including on/off ratio, subtheshold swing, and threshold voltage, of single-walled carbon nanotube field-effect transistors (SWNT-FETs). For the study, we utilize a unique device structure made of three adjacent Au electrodes, defined by electron-beam lithography, on doped-Si/SiO$_{2}$ substrates. A SAM of thiol molecules was formed selectively on one of side electrodes by dip-pen nanolithography. A single SWNT was then directed to assemble across the three electrodes, forming two FETs of essentially identical structure with the difference of the presence of the SAM at one of the electrodes of one FET. The device enables a direct unambiguous comparison of the electrical characteristics of the two SWNT-FETs with and without molecular modification of a Au electrode. We will present results of modification by molecules of different end-groups. Specifically, when one electrode was covered with 16-Mercaptohexandecanoic acid (MHA), a polar molecule, we observed a significant increase of the on/off ratio, decrease of the subthreshold swing, and shift of the threshold voltage for the SWNT-FET. [Preview Abstract] |
Wednesday, March 18, 2009 11:39AM - 11:51AM |
Q36.00003: Electrochemically mediated charge transfer effects in Single Walled Carbon Nanotubes (SWCNTS) Buddhika Abeyweera, Sharvil Desai, Gamini Sumanasekera Electrochemically mediated charge transfer has been studied by its effect on the surface conductivity of diamond. Here we show that the effect is not restricted to diamond, but may occur in other material systems as well, for example, semiconducting single-walled carbon nanotubes (s-SWNTs). For s-SWNTs the electron energies of the redox couple involving oxygen lie within or below the band gap. Nanotubes are known to be inherently n-type in vacuum and p-type under ambient conditions. Systematically sweeping the Fermi energy by controlled removal of oxygen through the redox couple and exposing to moist oxygen and ammonia with controlled pH, the charge transfer effect of the SWNTs was studied by \textit{in situ} monitoring of the Thermoelectric power (S) and Resistance (R). The changes in both R and S correlate very well with the relative position of the Fermi level with respect to the equilibrium chemical potential of the electrons. [Preview Abstract] |
Wednesday, March 18, 2009 11:51AM - 12:03PM |
Q36.00004: Does Moisture Influence the Chemical Detection of Gas Molecules Adsorbed on Single-Wall Carbon Nanotubes? Ming Yu, W.Q. Tian, C.S. Jayanthi, S.Y. Wu In this work, the role of water in the detection of hydrazine (N$_{2}$H$_{4})$ by a single-wall carbon nanotube (SWCNT) is investigated using first principles electronic structure calculations (DFT/GGA--USPP)[1]. This calculation is undertaken to interpret the experimental resistivity measurements for N$_{2}$H$_{4}$ adsorbed on SWCNT that reveal an $n$-type behavior [2]. Our preliminary theoretical studies of the adsorption of N$_{2}$H$_{4}$ on SWCNT revealed physisorption for N$_{2}$H$_{4}$ and an unaltered band structure for the SWCNT [3]. This prompted us to look into the role of water on the bonding of N$_{2}$H$_{4}$ to the SWCNT. We found that, by introducing a monolayer of water film on the (8,0) SWCNT, the adsorption of N$_{2}$H$_{4}$ can introduce occupied states near the Fermi level, exhibiting an $n$-type behavior. However, the introduction of just few water molecules was not sufficient to influence the electronic structure of N$_{2}$H$_{4}$/SWCNT. Presently, we are studying the influence of water films on the chemical detection of a variety of other gas molecules (N$_{2}$, NH$_{3, }$\textit{etc}.) by SWCNTs, and the results from such studies will also be reported. [1]. G. Kresse \textit{et al}. Phys. Rev. B \textbf{54}, 11169 (1996). [2]. S. Desai, \textit{et al}. (APS, March 2008). [3]. M. Yu, \textit{et al}. (APS, March 2008). [Preview Abstract] |
Wednesday, March 18, 2009 12:03PM - 12:15PM |
Q36.00005: ``Nanocavity'' Biochemical Sensor T. Kirkpatrick, J.I. Oh, P. Dhakal, D. Cai, H.Z. Zhao, A. Cimeno, L. Ren, K. Kempa, Z.F. Ren, T.C. Chiles, M.J. Naughton A biochemical sensor, based on a coaxial ``nanocavity,'' is described. The sensor is capable of detecting small changes in complex impedance, resulting from the presence of target entities in, and near, the device. Its nanoscale dimensions can be tuned for size-specificity, and its constituent components functionalized, for biochemical specificity. The measured capacitance of the bare sensor is in good agreement with calculations for a parallel array of 10$^{6}$/mm$^{2}$ vertically orientated coaxial capacitors. Here, changes in the complex impedance of the sensor are reported in the presence of various organic solvents. Molecules entering the coax annuli result in a significant change in impedance as a function of time, frequency and concentration. [Preview Abstract] |
Wednesday, March 18, 2009 12:15PM - 12:27PM |
Q36.00006: ABSTRACT WITHDRAWN |
Wednesday, March 18, 2009 12:27PM - 12:39PM |
Q36.00007: Optimizing the signal-to-noise ratio for biosensing with carbon nanotube transistors Iddo Heller, Jaan Mannik, Serge G. Lemay, Cees Dekker The signal-to-noise ratio (SNR) for real-time biosensing with liquid-gated carbon nanotube transistors is crucial for exploring the limits of their sensitivity, but has not been studied thus far. We show that, surprisingly, the maximum SNR is obtained when the device is operated in the sub-threshold regime. In the ON-state, additional contributions to the noise lead to a reduction of the SNR by up to a factor of 5. For devices with passivated contact regions, the SNR in ON-state is even further reduced than for bare devices. Interestingly, a conventional back gate provides a handle to improve the SNR in ON-state by increasing the conductivity of the contact regions. The results presented here demonstrate that biosensing experiments can best be performed in the sub-threshold regime for optimal SNR. [Preview Abstract] |
Wednesday, March 18, 2009 12:39PM - 12:51PM |
Q36.00008: Scanning Tunneling Microscopy of DNA-Carbon Nanotube Hybrids Dzmitry Yarotski, Svetlana Kilina, Alec Talin, Alexander Balatsky, Sergei Tretiak, Antoinette Taylor Production of carbon nanotube-based (CNT) devices holds a great promise for bringing the size of electronic circuits down to molecular scales. Recently, yet another step has been made towards achieving this goal by developing a new method for metal-semiconductor CNT separation, which relies on wrapping the CNT with ssDNA molecule[1]. Though it was shown that the outcome of the separation process strongly depends on the DNA sequence, further investigations have to be conducted to determine detailed structure of the hybrids and their electronic properties. Here, we use STM to characterize structural and electronic properties of the CNT-DNA hybrids and compare experimental results to theoretical calculations. STM images reveal 3.3 nm DNA coiling period, which agrees very well with the theoretical predictions. Additional width modulations with characteristic lengths of 1.9 and 2.6 nm are observed along the molecule itself. Although scanning tunneling microscopy confirms the presence of DNA in the hybrid and visualizes its structure, further experimental work is required to reveal the dependence of electronic properties of hybrids on their internal structure. [1] M. Zheng et al., Science 302, 1545 (2004). [Preview Abstract] |
Wednesday, March 18, 2009 12:51PM - 1:03PM |
Q36.00009: Electron Transport in Quasi-1D, DNA-Templated Nanoparticle Arrays M. S. Fairbanks, G. J. Kearns, B. C. Scannell, A. Loftus, R. P. Taylor, J. E. Hutchison Devices based on self-assembled metal nanoparticle arrays are good model systems for investigating the physics of the nanoscale regime, where size quantization effects and the Coulomb charging energy can dominate transport even at high temperatures. We apply a novel, highly parallel fabrication technique [1] that creates quasi-1D (200 nm x $\sim $20 nm) arrays of Au nanoparticles (r = 1.8 nm) bonded to DNA between predefined electrodes. These devices are found to exhibit Coulomb blockade over a wide range of operating temperatures (0.24 K to $>$80 K). We present an analysis of our results in comparison to recent theoretical predictions for 1- and 2D tunnel junction arrays and highlight some effects that arise from our devices' particular geometry. [1] M. G. Warner, J. E. Hutchison. Nature Materials 2, 272 (2003).; G. J. Kearns, et al. to be published. [Preview Abstract] |
Wednesday, March 18, 2009 1:03PM - 1:15PM |
Q36.00010: Determining the optical modes of solid and core-shell nanowires using relativistic electrons Jerome Hyun, Mark Levendorf, Martin Blood-Forsythe, Jiwoong Park, David Muller Nanowires serve as building-blocks for miniaturized optoelectronic devices. Determining the dispersion properties of the nanowires is necessary for device-engineering, but can be experimentally difficult with conventional optical techniques because of fundamental diffraction limitations. Fast electrons, on the other hand, can be focused to nanometer or sub-nanometer probes, providing spatial resolutions far superior to existing optical techniques. The time-varying Fourier components of the electron's evanescent electric field can extend beyond the far ultra-violet regime, providing a near-field, broad-band light source. Using scanning transmission electron microscopy and electron energy loss spectroscopy, we report on the relativistic calculations and measurements of the optical eigenmodes of single Ge nanowires. We also present calculations of a dielectric core/metallic shell system, where couplings between the surface plasmonic modes and the cavity modes occur. The work demonstrates a powerful optical characterization solution for nanowire systems. [Preview Abstract] |
Wednesday, March 18, 2009 1:15PM - 1:27PM |
Q36.00011: ABSTRACT WITHDRAWN |
Wednesday, March 18, 2009 1:27PM - 1:39PM |
Q36.00012: Transport properties of transition metal impurities on gold nanowires Renato B. Pontes, Edison Z. da Silva, Adalberto Fazzio, Ant\^{o}nio J. R. da Silva Performing first principles density functional theory (DFT) we calculated the electronic and transport properties of a Au thin nanowire with transition metal atoms (Mn, Fe, Ni or Co) bridging the two sides of the Au nanowire. We will show that these systems have strong spin dependent transport properties and that the local symmetry can dramatically change them, leading to a significant spin polarized conductance. This spin dependent transport is also associated with the transition metal in the nanowire, in particular with the d-level positioning. Using Co, for example [1], when the symmetry permits the mixing between the wire s-orbitals with the transition metal d-states, there are interference effects that resemble Fano-like resonances with an anisotropy of 0.07 at the Fermi level. On the other hand, if this symmetry decouples such states, we simply have a sum of independent transmission channels and the calculated anisotropy was 0.23. The anisotropies for the other transition metals, as well as calculated transmittances for two Co impurities will also be presented \textbf{[1] }R. B. Pontes, E. Z. da Silva, A. Fazzio and Ant\^{o}nio J. R. da Silva, J. Am. Chem. Soc. 130 (30), 9897-903, 2008 [Preview Abstract] |
Wednesday, March 18, 2009 1:39PM - 1:51PM |
Q36.00013: Quantum simulation of four-probe measurement of carbon nanotube Asako Terasawa, Keiji Tobimatsu, Tomofumi Tada, Satoshi Watanabe, Keiji Tobimatsu The four-probe method is widely used to measure the intrinsic resistance of various materials without the effects of sample-probe contacts. Recently, there have been many attempts to apply this method to nanoscale objects. Also, anomalous behaviors of nanoscale four-probe measurements were reported such as the negative four-probe resistance of single-walled carbon nanotube. To investigate quantum effects on the four-probe measurements in nanoscale, we examined the four-probe resistance of (5,5)-carbon nanotube with a vacancy or without a vacancy theoretically on the basis of density functional tight-binding method and Green's function method. We found that the calculated four-probe resistance is sensitive to the position of the vacancy relative to the probes even when the sample-probe connections are weak. Such a behavior is unlikely to be seen in the two-probe resistance, and suggests that the four-probe resistance of nanoscale systems depend on the sample-probe geometry in a complicated manner. [Preview Abstract] |
Wednesday, March 18, 2009 1:51PM - 2:03PM |
Q36.00014: Coherent Acoustic Spectroscopy of Nanorod Arrays Masashi Yamaguchi, Jianxun Liu, Dexian Ye, Toh-Ming Lu Coherent acoustic transport through vertically grown nanorod array on substrate and coherent acoustic vibration of nanorod arrays are experimentally studied by using femtosecond laser based acoustic spectroscopy in GHz-THz frequency range. In nanorod materials, acoustic phonon dispersion and life time are altered by the spatial confinement, and many of nanoscale materials have mechanical resonance in GHz-THz frequency range. Si and Ni nanorod arrays are grown vertical on top of a thin Al transducer layer deposited on substrate. Longitudinal acoustic phonons are excited coherently in the transducer layer. We have observed the transport of the coherent acoustic pulses through the nanorod arrays. The center frequency of the acoustic pulse was comparable to the diameter of the nanorods. Also, we have observed the transfer of the acoustic energy to the nanorod vibration mode while the coherent acoustic pulse propagates through. Mean-Free-Path and time of flight of the coherent acoustic phonons is determined by comparing the results of the samples with different thicknesses. [Preview Abstract] |
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