Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session W31: Nanotubes: Devices |
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Sponsoring Units: DCMP Chair: Kris Andersen, Naval Research Laboratory Room: Baltimore Convention Center 328 |
Thursday, March 16, 2006 2:30PM - 2:42PM |
W31.00001: High On-Currents in Doped Schottky-Barrier Nanotube Transistors Yung-Fu Chen, Michael Fuhrer For many contact metals, the short channel single-walled carbon nanotube field-effect transistor (SWNT-FET) has been understood as a ballistic Schottky barrier-FET (SB-FET), in which high on- currents may be realized with thin gate dielectrics through narrowing of the SB by the gate field [1]. Recently Ohmic contacts to nanotubes have been achieved through the use of high work function metals; such devices show high on-currents and near-ideal subthreshold swings [2]. Here we demonstrate that SWNTs in ambient on SiO$_{2}$ are p-doped. Doped SB-SWNT- FETs exhibit high on-currents due to thinning of the SB by doping, but retain the poor subthreshold behavior of SB-FETs. Dopants in SWNT-FETs can be removed by applying up to 50 V drain bias in vacuum, corresponding to dissipated power of $>$ 1 mW. Undoped devices exhibit much lower on-currents, and intrinsic, ambipolar behavior with symmetric SB. This work is supported by National Science Foundation under Grant No. 0102950. [1] S. Heinze, et al., Phys. Rev. Lett. 89, 106801 (2002). [2] A. Javey, et al., Nature 424, 654 (2003). [Preview Abstract] |
Thursday, March 16, 2006 2:42PM - 2:54PM |
W31.00002: Temperature and Carrier-Density Dependence of 1/f Noise in Single-walled Carbon Nanotube Transistors David Tobias, Masa Ishigami, C.J. Lobb, Michael S. Fuhrer Field-effect transistors (FETs) have been fabricated from individual semiconducting single-walled carbon nanotubes (SWNTs) grown by chemical vapor deposition on SiO$_{2}$/Si substrates and contacted by metal (Cr/Au) electrodes. We have measured the low-frequency anomalous noise (1/f noise) in such SWNT-FETs as a function of temperature and charge carrier density. This material is based upon work supported by the National Science Foundation under Grant No. 0102950 and the Center for Superconductivity Research. [Preview Abstract] |
Thursday, March 16, 2006 2:54PM - 3:06PM |
W31.00003: Optical switching of functionalized carbon nanotube transistors Julien Borghetti, Vincent Derycke, Pascale Chenevier, Arianna Filoramo, Marcello Goffman, Jean-Philippe Bourgoin, Stephane Lenfant, Dominique Vuillaume Carbon Nanotube (CNT) transistors can emit or detect photons at wavelengths defined by the CNT chirality. To extend their capabilities in optoelectronics, it is important to be able to tune this wavelength independently of the CNT structure. A way to achieve such a goal is to chemically functionalize the CNT. In the present study, we demonstrate that drastic photo-induced modifications of the electrical characteristics of self-assembled CNT transistors functionalized by photoactive polymers can be achieved. We show that the polymer film acts as a wavelength dependent 'optical gate', which is much more efficient than a conventional electrostatic gate and can induce changes in conductance exceeding four orders of magnitude. The switching mechanism involves the creation and separation of photo-excited charges in the polymer, the spatial distribution and relaxation rates of which are studied taking advantage of the very high charge sensitivity of the CNT transistor. [Preview Abstract] |
Thursday, March 16, 2006 3:06PM - 3:18PM |
W31.00004: Large Area Aligned Arrays of SWNTs for High Performance Thin Film Transistors. Coskun Kocabas, Seong Jun Kang, John Rogers This talk will emphasize a convenient method for generating large scale, horizontally aligned arrays of pristine, single walled carbon nanotubes (SWNTs).~ The approach uses guided growth, by chemical vapor deposition (CVD), of SWNTs on Y-cut single crystal quartz substrates.~ Studies of the growth reveal important relationships between the density and alignment of these tubes, the CVD conditions and the morphology of the quartz.~ Electrodes and dielectrics patterned on top of these arrays yield thin film transistors (TFTs) that use the SWNTs as effective thin film semiconductors.~ Channel length scaling of device mobility, on current and off current provide insights into the transport characteristics. Combining the aligned arrays with random networks, which are grown simultaneously through the use of patterned catalysts, yields `all-tube' based devices.~ The ability to build high performance devices of this type suggests significant promise for large scale aligned arrays of SWNT in electronics, sensors and other applications. [Preview Abstract] |
Thursday, March 16, 2006 3:18PM - 3:30PM |
W31.00005: Field-Effect Transistors Assembled From Functionalized Carbon Nanotubes Christian Klinke, James Hannon, Ali Afzali, Phaedon Avouris We have fabricated field effect transistors from carbon nanotubes using a novel selective placement scheme. We use carbon nanotubes that are covalently bound to molecules containing hydroxamic acid functionality. The functionalized nanotubes bind strongly to basic metal oxide surfaces, but not to silicon dioxide. Upon annealing, the functionalization is removed, restoring the electronic properties of the nanotubes. The devices we have fabricated show high ON current (about 1 uA) and an ON/OFF ratio of more than 1e6. [Preview Abstract] |
Thursday, March 16, 2006 3:30PM - 3:42PM |
W31.00006: Template-directed Self-assembly of Carbon Nanotube Field-Effect Transistors Stephen McGill, Saleem Rao, Pradeep Manandhar, Seunghun Hong, Peng Xiong We pattern self-assembled monolayers (SAMs) of organic molecules to control the interactions between carbon nanotubes and inorganic surfaces. Deposition of the SAMs forms a template that directs the placement and alignment of nanotubes on lithographically defined electrodes to create field-effect transistors (FETs). Our assembly process is highly scalable and we demonstrate parallel fabrication of five FETs on a single substrate. These FETs exhibit large ``on'' currents of $\sim $1$\mu $A with ``on/off'' ratios as high as 10$^{6}$. Furthermore, our devices exhibit novel functionality by operating hysteresis-free without passivation of the nanotube or electrode surfaces. These features may lead to enhanced performance for delicate sensing applications utilizing these devices. We discuss the electrical characteristics of these FETs and contrast them with other state-of-the-art devices and assembly strategies. This work has been supported by NSF NIRT grant ECS-0210332. [Preview Abstract] |
Thursday, March 16, 2006 3:42PM - 3:54PM |
W31.00007: Gas Sensitivity of Carbon Nanotube Devices J. H. Chen, Masa Ishigami, M. S. Fuhrer, E. D. Williams We have measured the gas sensitivity of field effect transistors made from individual single-walled carbon nanotubes in an ultra high vacuum environment. We exposed nanotube devices to varying partial pressures of oxygen and argon. We will compare the results to existing theoretical calculations for oxygen sensitivity of carbon nanotubes and discuss the ultimate gas sensitivity for these devices. [Preview Abstract] |
Thursday, March 16, 2006 3:54PM - 4:06PM |
W31.00008: Single Walled Carbon Nanotube-based Aqueous Sensors Sarah Lastella, Aravind Vijayaraghavan, Swastik Kar, Pulickel M. Ajayan, Chang Y. Ryu Single walled carbon nanotube (SWNT) field effect transistors (FETs) have been utilized as chemical specific sensors by incorporating a sensitizing agent into the nanotube sidewalls. Here we report the non-covalent sidewall functionalization of SWNT FETs through the adsorption of macro-organic molecules. The modified SWNT FETs recognize changes in pH and oxidation states through a change in current flow across the devices. These uniformly dispersed nanotubes, grown directly on the FET substrate prior to electrode deposition, enhance the available tube surface area for molecular adsorption, and thus enhance the signal sensitivity. [Preview Abstract] |
Thursday, March 16, 2006 4:06PM - 4:18PM |
W31.00009: Atomic Nanotube Welders. Morinobu Endo, Hiroyuki Muramatsu, Takuya Hayashi, Yoong-Ahm Kim, Gregory Van Lier, Jean-Christophe Charlier, Humberto Terrones, Mildred S. Dresselhaus, Mauricio Terrones We demonstrate that the incorporation of boron between double walled carbon nanotubes (DWNTs) during thermal annealing results in covalent nanotube ``Y'' junctions, DWNT coalescence and the formation of flattened multi-walled carbon nanotubes (MWNTs). The processes occur via the merging of adjacent tubes which is triggered by B interstitial atoms. In order to demonstrate the unique welder properties of B in the process, we have carried out \textit{AM1} molecular dynamics simulations at high temperatures and \textit{ab-initio }calculations. We observe that B atom interstitials between DWNTs are responsible for the rapid establishment of covalent connections between neighboring tubes (polymerization). Once B is in the lattice, tube faceting (polygonization) starts to occur, and the electronic properties are expected to change dramatically. [Preview Abstract] |
Thursday, March 16, 2006 4:18PM - 4:30PM |
W31.00010: Quantized conductance observed in reversible atomic contacts fabricated by template electroplating using an on-membrane anode Zuxin Ye, Wenhao Wu We report a new template electroplating method for fabricating reversible atomic contacts between a long nanowire and a macroscopic contact pad. In comparison to a typical template method using a standing-alone anode, we directly evaporate the anode on one of the porous membrane surfaces. Single nanowires, upon emerging from the pores, make reversible atomic contacts with the on-membrane anode via a self-terminating mechanism. Quantized conductance steps have been observed in a controlled fashion during deposition and dissolution. This method can potentially be applied for the controlled fabrication and integration of nanowires, point contacts, and nanosized interconnects in template-based nanofabrication. [Preview Abstract] |
Thursday, March 16, 2006 4:30PM - 4:42PM |
W31.00011: Structural and Transport Properties of Dielectrophoretically Assembled Interconnects Birol Ozturk, Ishan Talukdar, Prem Thapa, Charles Blackledge, Daniel Grischkowsky, Bret Flanders Dielectrophoresis was used to form $\sim $140nm diameter interconnects composed of gold nanorods between targeted points in a circuit. Cleanroom-based lithographic procedures were used to produce identical arrays of electrodes, improving the sample-to-sample reproducibility of the interconnect-conductances to $\sim $10{\%}. Transmission electron microscopy and low temperature conductivity analyses indicate that the Coulomb Blockade associated with the individual nanorods is the primary conductance-limiting feature. To further improve the reproducibility of the structural and transport properties of dielectrophoretic interconnects, we investigate submicron wire formation in aqueous solutions of indium acetate. Our preliminary data show that single crystal wires with submicron diameters may be fabricated from such solutions. [Preview Abstract] |
Thursday, March 16, 2006 4:42PM - 4:54PM |
W31.00012: DNA-Functionalized Carbon Nanotubes for Chemical Sensing M. Chen, C. Staii, S. Khamis, A.T. Johnson, J.E. Fischer, A Gelperin We demonstrate nanoscale sensors based on single-stranded DNA (ss-DNA) as the chemical recognition site and single-walled carbon nanotube field effect transistors (swCN-FETs) as the electronic readout component. SwCN-FETs functionalized with ss-DNA respond to gaseous analytes that do not cause a detectable current change in bare swCN-FETs. The response differs in sign and magnitude depending on the type of analyte and the DNA base sequence. The sensors maintain a constant response through at least 50 air-analyte cycles, and have response and recovery times on the scale of seconds. Furthermore, ss-DNA is found to chemically gate swCN-FET. The analytes used are found to interact with both the nanotube and the substrate. This sensor is promising for electronic olfaction systems consist of coupled sensor arrays and an odor recognition algorithm. Applications range from homeland security to disease diagnosis. [Preview Abstract] |
Thursday, March 16, 2006 4:54PM - 5:06PM |
W31.00013: Electrical transport behavior of all - carbon nanotube - based three terminal junctions Yun-Hi Lee, Je-Min Yoo, Jong-Hee Lee In this study, we propose a process for suspended \textit{in situ} lateral growth of all - carbon nanotube(CNT) based junction and report on the high current capacity of the CNT junction, especially, its current (I) response characteristics with and after UV. Furthermore, the analogy between current suppression and reversible switching of capacitor was studied by capacitance(C) spectroscopy. The designed diluted magnetic impurity doped oxide film was adopted as catalyst for the fabrication of all - CNT-based junction. 40 suspended junctions was tested and normally, one junction produced current of a few uA/1um at room temperature. The suspended CNT with the same electrode materials is expected to operate with ambipolarity. The nearly same low barrier height for the hole and electron conduction was estimated via I-T(K) measurements. Also, the surface of CNT was easily cleaned by low intensity UV treatment, resulting in a highly conductive channel that showed high current carrying behavior. Our result can be applied to develop a practical, accessible system for forming reproducible nanoelectronic junctions as well as to accelerate the realization of all low dimensional molecular devices. [Preview Abstract] |
Thursday, March 16, 2006 5:06PM - 5:18PM |
W31.00014: Energy Conversion Efficiency in Nanotube Optoelectronics Fran\c{c}ois L\'{e}onard, Derek Stewart We present theoretical performance estimates of nanotube optoelectronic devices under bias. Current-voltage characteristics of illuminated nanotube {\it p}-{\it n} junctions are calculated using a self-consistent non-equilibrium Green's function approach. Energy conversion rates in the tens of percent range are predicted for incident photon energies near the band gap energy. In addition, the energy conversion rate increases as the diameter of the nanotube is reduced, even though the quantum efficiency shows little dependence on nanotube radius. These results indicate that the quantum efficiency is not a limiting factor for use of nanotubes in optoelectronics. [Preview Abstract] |
Thursday, March 16, 2006 5:18PM - 5:30PM |
W31.00015: A Novel Nanotube-on-Insulator (NOI) Approach toward Single-Walled Carbon Nanotube Devices Chongwu Zhou, Xiaolei Liu, Daihua Zhang We present a novel nanotube-on-insulator (NOI) approach to produce high-yield nanotube devices based on aligned single-walled carbon nanotubes. First, we managed to grow aligned nanotube arrays with controlled density on crystalline, insulating sapphire substrates, which bear analogy to industry-adopted silicon-on-insulator substrates. Based on the nanotube arrays, we demonstrated registration-free fabrication of both top-gated and polymer-electrolyte-gated field-effect transistors with minimized parasitic capacitance. In addition, we have successfully developed a way to transfer these aligned nanotube arrays to flexible substrates. Our approach has great potential for high-density, large-scale integrated systems based on carbon nanotubes for both micro- and flexible electronics. [Preview Abstract] |
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