Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session L27: Focus Session: Carbon Nanotubes: Devices |
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Sponsoring Units: DMP Chair: Christian Schoenenberger, University of Basel Room: LACC 501C |
Tuesday, March 22, 2005 2:30PM - 3:06PM |
L27.00001: Advanced Sensors based on Carbon Nanotube Networks Invited Speaker: Single wall carbon nanotubes (SWNTs) are useful materials for a variety of electronic applications. The relative chemical passivity and environmental robustness of SWNTs suggests that they could be suitable materials for environmental sensors. Kong et al. * have demonstrated sensing of biological and chemical analytes from liquid and gaseous ambient, respectively. We have extended this work in several ways. An important criterion for sensors is the noise level, which sets a lower limit on sensitivity. It is shown that one of the weaknesses of nanoscale devices prepared from discrete SWNTs, high 1/f noise, is greatly ameliorated by the use of interconnected random networks of SWNTs to make large, or ``macro'' scale, devices. While changes in conductance can be used to indicate the presence of adsorbates of volatile analytes, it is shown that a capacitor configuration, utilizing the carbon nanotube network (CNN) as one electrode, leads to a much more sensitive, responsive, and accurate detector, suitable for use with a wide range of materials. In general, the capacitance of such a detector is proportional to the ambient fraction of equilibrium vapor pressure times the dipole moment of molecules constituent in ambient. Thus, saturated atmospheres of extreme low-vapor pressure polar materials (e.g., explosives) can induce responses greater than below-saturation atmospheres of highly volatile materials, or even saturated atmospheres of non-polar materials. This response can be further enhanced by the deposition of self-assembled monolayer or ultra-thin polymer coatings on the CNN or device substrate. Use of such modifications allows specificity, by comparing responses from each of a set of modified sensors to challenge. *J. Kong, N.R. Franklin, C.Ahou, M.G. Chapline, S. Peng, K. Cho, and H. Dai, Science \underline {87}, 622 (2000). [Preview Abstract] |
Tuesday, March 22, 2005 3:06PM - 3:18PM |
L27.00002: Tunable Carbon Nanotube Tunneling Devices for Wireless Communications Jaewu Choi, Youngsik Song Carbon nanotube could be one of the best candidates for a nanoscale emitter, a receiver, and a mechanical switch, which are essential components for the future application of high-speed wireless communications. Tunable nanoscale resistors, capacitors, inductors, and mechanical resonators can be implemented with carbon nanotubes. It is originated from the excellent properties of carbon nanotube such as structure dependent metallic properties, pseudo-one-dimensional transport characteristics and electronic structure, hollow structure, extremely high mechanical strength with high aspect ratio, good thermal conductivity, chemical inertness, etc. In this study, we studied carbon nanotubes as an emitter, a receiver and an electromechanical oscillator from suspended carbon nanotubes on a device array for the wireless communications. The suspended carbon nanotube arrays are fabricated by directly and laterally grown carbon nanotubes on the multilayer electrode arrays with a field effect transistor structure. The characteristics of carbon nanotube transmitter, receiver, and mechanical oscillator are studied using an impedance analyzer as a function of frequency and gate voltage modulation. [Preview Abstract] |
Tuesday, March 22, 2005 3:18PM - 3:30PM |
L27.00003: Impedance Spectroscopy, High Frequency Scanning Gate Microscopy and Local Memory Effect of Carbon Nanotube Transistors Cristian Staii, Rui Shao, Dawn A. Bonnell, Alan T. Johnson Successful implementation of carbon nanotube field effect transistors (CNFETs) as nanoelectronic devices requires reliable techniques for the characterization of their local electronic properties. At low frequencies, this goal was achieved by using recently developed scanning probe techniques such as Scanning Gate Microscopy (SGM). The extension of these techniques to high frequency is important because, although the low frequency performance of CNFET has been greatly improved, little is known about their high frequency behavior. We will present impedance characteristics of CNFET devices for ac-frequencies up to 15MHz. We also extend SGM to frequencies up to 15MHz, and use it to image changes in the impedance of CNFET circuits induced by the SGM-tip gate. Results of both experiments are consistent with a simple RC parallel circuit model of the CNFET, with a time constant of 0.3 microsec. We also use the tip gate to show that charge injection from the single wall nanotube into the substrate, which is responsible for the memory effect, can be induced at specific locations along the tube length. This result is a strong indication that CNFET-based memory cells may be miniaturized to dimensions far below the micrometer scale of current devices. [Preview Abstract] |
Tuesday, March 22, 2005 3:30PM - 3:42PM |
L27.00004: Nanowire and nanotube transistors with surrounding gates Zhicheng Luo, Bo Lei, Xiaolei Liu, Chao Li, Chongwu Zhou We will present fabrication and electronic transport studies of novel nanowire and nanotube transistors with surrounding polymer-electrolyte gates. These devices are based on nanowires/nanotubes contacted by source/drain electrodes atop Si/SiO$_{2}$ substrate. Vias were etched through the SiO$_{2}$ layers, followed by refilling LiClO$_{4}$/poly(ethylene oxide). The silicon substrate is thus in electrical contact with the polymer electrolyte, therefore forming the surround gate for the transistors. Electronic characterization revealed well-enhanced transconductance for both nanowire and nanotube transistors, with operating gate voltage reduced to 1V. In addition, intriguing negative differential resistance has been observed with surround-gated nanowire transistors, which can be attributed to the much enhanced gate dependence. [Preview Abstract] |
Tuesday, March 22, 2005 3:42PM - 3:54PM |
L27.00005: Single-nanotube Devices from Purified HiPCO Material Danvers E. Johnston, M. F. Islam, Arjun G. Yodh, A. T. Johnson We have developed a purification process that retains the remarkable electronic properties of single walled carbon nanotube (SWNT) material. Nanotubes grown by the HiPCO method (High Pressure catalytic decomposition of Carbon monOxide) are purified and suspended as single tubes and small bundles in a surfactant solution. SWNTs are deposited on functionalized substrates and contacted by electrodes. The resulting circuits consist of high quality metallic and semiconducting nanotubes that are apparently unaffected by the purification process. Circuits made from raw HiPCO material have vastly inferior device parameters indicating the crucial role of the purification process. We show how source-drain current measurements as a function of temperature and backgate voltage can be used to determine the energy gap of a semiconducting nanotube in a field effect transistor geometry. This work represents significant progress towards the goal of producing complex integrated circuits from bulk-grown SWNT material. This work has been partially supported by NSF (Grants DMR 00- 79909 (MRSEC); DMR-0203378), by NASA (NAG8-2172), and the Petroleum Research Fund. DJ acknowledges support from an NSF- funded IGERT Fellowship Grant DGE-0221664 administered through Penn's Center for the Science and Engineering of Nanoscale Systems. [Preview Abstract] |
Tuesday, March 22, 2005 3:54PM - 4:06PM |
L27.00006: Thin Film Carbon Nanotube FETs with Polymer Electrolytes Taner Ozel, Anshu Gaur, John Rogers, Moonsub Shim Thin film transistors of single-walled carbon nanotubes were operated with polymer electrolyte as gate media. Nearly ideal gate efficiencies allow low-voltage operation with the absence of the common hysteresis problem observed in back-gated carbon nanotube FETs yielding a reliable and simple method for measuring the device characteristics. Furthermore, the conduction type (p/n-type) of the devices can easily be controlled by varying the electrolyte media. Effects such as charge transfer between polymer and nanotubes, and tube-tube interactions in arrays of nanotubes will be discussed. [Preview Abstract] |
Tuesday, March 22, 2005 4:06PM - 4:18PM |
L27.00007: Long, Suspended Metallic and Semiconducting Carbon Nanotube Devices Todd Brintlinger, Michael S. Fuhrer We have fabricated devices consisting of individual suspended carbon nanotubes (CNTs) spanning trenches up to 120$\mu $m long and 500$\mu $m deep. The carbon nanotubes are grown via chemical vapor deposition over existing gold or platinum electrodes, forming complete electronically addressable devices without exposure of the CNTs to resists or etchants. These CNT devices allow study of the intrinsic transport properties of the nanotubes without disorder induced by the substrate or chemical residues from conventional lithography. The use of a mobile probe as a gate electrode allows identification of metallic and semiconducting nanotubes. We present the growth and fabrication procedures along with transport measurements on these long, suspended CNTs. [Preview Abstract] |
Tuesday, March 22, 2005 4:18PM - 4:54PM |
L27.00008: Exploiting the Unique Properties of Nanotubes for Nanoelectromechanical Systems Invited Speaker: |
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L27.00009: A Three-Terminal Carbon Nanorelay Y.W. Park, S.W. Lee, D.S. Lee, S.H. Jhang, R.E. Morjan, M. Sveningsson, O.A. Nerushev, Eleanor E.B. Campbell Three-terminal nanorelay structures were fabricated with multiwall carbon nanotubes (MWNTs). The nanotube relays were deflected by applying a gate voltage until contact (mechanical and/or electrical) was made with a drain electrode, thus closing the circuit. It was possible to achieve multiple switching cycles, showing that carbon nanotubes are suitable and practical systems for developing nanoelectromechanical devices of this kind. [Preview Abstract] |
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L27.00010: Carbon Nanotubes as the Protective Coating in Space Propulsion Systems Yoke Khin Yap, Jitendra Menda, Vijaya Kayastha, Lakshman Vanga, Jiesheng Wang, Alex Kieckhafer, Dean Massey, Lyon King, Svetlana Dimovski, Yury Gogotsi We have evaluated carbon nanotubes as the protective coatings against ion erosion in space propulsion systems. The space exploration program faces enormous challenges to achieve improvements in safety, cost, and speed of missions. Electric propulsion (EP) thrusters are recognized as far more efficient than chemical thrusters. However, an electrode sputter erosion process limits the lifetimes of these EP devices. Inspired by their impressive cohesive energy and stiffness, we have tested carbon nanotubes (CNTs) as the protective coating. We compare CNTs to CVD diamond, carbon and BN films as exposed to the exhaust beam of a Hall-effect thruster. We found that only CVD diamond films and VA-MWNTs survived erosion by 250 eV ions. Analysis by field emission scanning electron microscopy, backscattered electron imaging, and Raman spectroscopy indicate that these VA-MWNTs were bundled at their tips before the erosion. An erosion mechanism was then formulated and verified by a series experiments with Xe propellant at an ion current density of 5 mA/cm$^{2}$. We found that VA-MWNTs are eroded in a nonlinear rate. Our result suggests that catalysts on the VA-MWNTs are responsible for this erosion and their removal could further enhance the resistance of VA-MWNTs against ion erosion. [Preview Abstract] |
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