Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session Y7: Challenges and Issues in Nanowire Nanodevices |
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Sponsoring Units: DCMP Chair: Paul S. Weiss, Pennsylvania State University Room: Baltimore Convention Center 307 |
Friday, March 17, 2006 8:00AM - 8:36AM |
Y7.00001: Nanowires for High-Performance Integrated Macroelectronics Invited Speaker: Extensive electrical and optical characterization has shown that single-crystal semiconductor nanowires display physical properties that match or exceed those of their bulk counterparts. In addition, our studies have shown that it is possible to manipulate and assemble high-performance devices using low-temperature liquid based processes. These high-performance semiconductor device properties and unconventional processing advantages possible with nanowires can be readily applied in the field of macroelectronics, where integrated devices are patterned over large noncrystalline and/or flexible substrates. The separation of high temperature nanowire synthesis from subsequent ambient temperature assembly allows for electronic devices of varied functionality to be fabricated on virtually any substrate. We have fabricated p-Si nanowire transistors on glass and plastic substrates that display parameters rivaling those of single crystal silicon and exceeding those of state-of-the-art amorphous silicon and organic transistors currently used for flexible electronics on plastic substrates today. With the improved reproducibility obtained through improvements in nanowire growth and the use of multi-nanowire transistors, we have been able to demonstrate integrated logic structures with gain up to megahertz frequencies. On-chip integration of nanowire-based inverters was accomplished in a fully parallel process, and has enabled the fabrication of inverters and ring oscillators with frequencies up to 200 MHz, the highest observed for circuits based on nanoscale materials. [Preview Abstract] |
Friday, March 17, 2006 8:36AM - 9:12AM |
Y7.00002: Property of individual conducting-polymer nanowires: conductance and FET devices Invited Speaker: Electronic devices using organic molecules and nanowires have been intensively studied in dream of a smart life utilizing charming functions of organic materials, that are thin, light, flexible and yet inexpensive and safe for environment. A key step for measuring the property of organic nanowires and evaluating the performance of the nanowire devices is how to access them by appropriate nanoscopic methods. Scanning probe microscopy (SPM) based nanofabrication (SP nanofabrication) has been used to fabricate two- or four-probe fine electrodes and several kinds of nanowires made of conducting polymers have been evaluated by SPM and the fine electrodes made with Pt thin film fabricated on SiO2/doped Si or sapphire substrates [1,2]. We have tested conductivity of single poly (3,4-ethylenedioxythiophene) / poly (styrenesulfonate) (PEDOT/PSS) nanowires. After cutting each nanowires placed on the fine electrodes, the current was checked and we were able to confirm that the conductivity was derived from the PEDOT nanowires themselves. The temperature dependence of the conductivity was explained by the quasi one-dimensional variable range hopping (VRH) model. We also will discuss on the field-effect-transistor (FET) made of a single nanowire. In collaboration with: S. Heike, M. Fujimori, Y. Suwa (ARL), H. Ichihara, S. Samitsu, A. Inomata, T. Shimomura, K. Ito (Univ. Tokyo), K. Miki, T. Ohno (NIMS), H. Mizuseki (IMR), Y. Terada, H. Shigekawa (Univ. Tsukuba). [1] J. P. Hill, W. Jin, A. Kosaka, T. Fukushima, H. Ichihara, T. Shimomura, K. Ito, T. Hashizume, N. Ishii, and T. Aida, Science 304, 1481 (2004). [2] S. Samitsu, T. Shimomura, K. Ito, S. Heike, M. Fujimori, S. Heike, and T. Hashizume, Appl. Phys. Lett., 86, 233103 (2005). [Preview Abstract] |
Friday, March 17, 2006 9:12AM - 9:48AM |
Y7.00003: Magnetic field asymmetry and high temperature magnetoresistance in single-walled carbon nanotubes Invited Speaker: The length scales and scattering processes in the one-dimensional electron system in single-walled carbon nanotubes remain only partially understood. Measuring the magnetoresistance, in both linear and nonlinear response, is a way to investigate these processes. In disordered nanotubes with ballistic paths much shorter than the length, we observe magnetoresistance in the metallic regime which at low temperatures resembles the universal fluctuations and weak localization seen in higher dimensional metals. A parabolic magnetoresistance persists at room temperature, indicating a significant role for phase coherence and/or interactions at high temperatures. While the linear resistance of a two-terminal sample must be an even function of magnetic field $B$ by Onsager's principle, the nonlinear resistance need not be. Importantly, the $B$-asymmetric nonlinear terms can in principle be used to infer the strength of electron-electron interactions in the sample [1]. We have therefore also measured in detail the lowest order $B$-asymmetric current contributions, with a focus on the $B$-linear term. This has apparently not been done before in any system. Consistent with general theory, at high temperatures the term is small and has a constant sign independent of Fermi energy. At low temperatures it grows and develops mesoscopic fluctuations. Although these result imply that interactions are involved in the transport, calculations specific to nanotubes are needed in order to extract interaction parameters. This work was done by the authors of Ref [2]. \textit{References:} [1] E.L. Ivchenko and B. Spivak, Phys. Rev. B 66, 155404 (2002); [2] Jiang Wei, Michael Shimogawa, Zenghui Wang, Iuliana Radu, Robert Dormaier, and David H. Cobden, Phys. Rev. Lett. (Dec. 2005) (cond-mat/0506275). [Preview Abstract] |
Friday, March 17, 2006 9:48AM - 10:24AM |
Y7.00004: Electrical Conductivity of Organic and Inorganic Nanowires Measured by Multi-probe Scanning Tunneling Microscopes Invited Speaker: Since 1998 [1], the authors and co-workers have developed multi-probe scanning tunneling microscopes (MPSTMs), in which two, three or four probes are operated independently. All probes of the MPSTMs can observe STM images independently, but the main role of the multiple probes is to be used as nanoscale electrodes that can contact any points selected in an observed STM image. It is therefore possible to measure electrical conductivity at the nanoscale through the multiple probes. By using MPSTMs and related methods, we measured the electrical conductivity of organic and inorganic nanowires, i.e., single-wall carbon nanotubes (SWCNTs), erbium disilicide (ErSi2) metallic nanowires, and single polydiacetylene (PDA) molecular wires. For a SWCNT and an ErSi2 nanowire, ballistic conduction was observed at lengths less than about 500 and 20 nm, respectively, at room temperature. For a PDA molecular wire, polaron formation due to charge injection caused by applying a voltage to an STM tip placed close to the PDA molecular wire was observed, and when the voltage exceeded a critical value, the PDA molecular wire changed into a metallic state. [1] M. Aono, C.-S. Jiang, T. Nakayama, T. Okuda, S. Qiao, M. Sakurai, C. Thirstrup, Z.-H. Wu: Oyo Buturi (Applied Physics) \underline {67}, 1361 (1998) (in Japanese); A brief English abstract is available on INSPEC. [Preview Abstract] |
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