Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session A14: Focus Session: Molecular-Scale Electronics and Sensors I |
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Sponsoring Units: FIAP DCP Chair: Vince McKoy, Caltech Room: LACC 403B |
Monday, March 21, 2005 8:00AM - 8:36AM |
A14.00001: Electronics at the molecular level Invited Speaker: In the early 1970s, Aviram and Ratner suggested the notion that molecular configurations might be used to carry and rectify electronic current. This notion was put forward well before its time, for today, some thirty years later, with the remarkable progress in nano tool development and material process capabilities, the concept of electronic conduction in molecular systems is now being experimentally tested in laboratories around the world. Correspondingly, over the years, there has been a substantial effort in the theoretical modeling of molecular configurations which has shed enormous light on the atomic details of the electron transport processes at the molecular level. The idea of considering electronic functionality at the molecular scale is not a surprise; it was very much embodied in Feynman's early vision captured in ``There's Plenty of Room at the Bottom,'' and has always been part of the speculative horizon of Moore's law. Visionaries often speculate about the possibilities and opportunities to emerge from the molecular scale; but the challenges and barriers to success and realizability are substantial. The intention of this presentation is to discuss some of the basic possibilities and limitations of molecular scale electronics. Further, the presentation incorporates some of our recent quantum modelings on connected molecular systems; here we model metal contacts to molecular clusters in an {\em exact} framework using a molecular self-consistent field approach so as to calculate realistic, electric field dependent transport properties for the molecular system, and to study the role of the contact-molecule interface in influencing the transport properties of the entire molecular system. [Preview Abstract] |
Monday, March 21, 2005 8:36AM - 9:12AM |
A14.00002: Constructing a Computer from Molecular Components Invited Speaker: Constructing a Computer from Molecular Components Research efforts directed toward constructing a molecular computer will be described in the context of recent developments in nanotechnology. Routes will be outlined from the synthesis of the basic building blocks such as wires and alligator clips, to the assembly of the processing functional blocks. Specific achievements include: (1) isolation of single molecules in alkane thiolate self-assembled monolayers and addressing them with an STM probe, (2) single molecule conductance measurements using a mechanically controllable break junction, (3) 30 nm bundles, approximately 1000 molecules, of precisely tailored molecular structures showing negative differential resistance with peak-to-valley responses far exceeding those for solid state devices, (4) dynamic random access memories (DRAMs) constructed from 1000 molecule units that possess 15 minute information hold times at room temperature, (5) demonstration of single-molecule switching events and (6) initial assemblies and programming of molecular CPUs in a NanoCell configuration that show room temperature electronic memory with days or electronic hold time, and the programming of logic gates such as AND, OR, NAND and NOR gates. Full silicon-molecule interfaces are used in the generation 3 NanoCell, as well as molecular FETs (MoleFETs). Finally, a molecular testbed has been developed that involves only semiconductor contacts (no metal contacts) to the molecules, thereby mitigating electromigration. [Preview Abstract] |
Monday, March 21, 2005 9:12AM - 9:24AM |
A14.00003: CMOL: A New Concept for Nanoelectronics Konstantin Likharev I will review the recent work on devices and architectures for future hybrid semiconductor/molecular integrated circuits, in particular those of ``CMOL'' variety [1]. Such circuits would combine an advanced CMOS subsystem fabricated by the usual lithographic patterning, two layers of parallel metallic nanowires formed, e.g., by nanoimprint, and two-terminal molecular devices self-assembled on the nanowire crosspoints. Estimates show that this powerful combination may allow CMOL circuits to reach an unparalleled density (up to 10$^{12}$ functions per cm$^{2})$ and ultrahigh rate of information processing (up to 10$^{20}$ operations per second on a single chip), at acceptable power dissipation. The main challenges on the way toward practical CMOL technology are: (i) reliable chemically-directed self-assembly of mid-size organic molecules, and (ii) the development of efficient defect-tolerant architectures for CMOL circuits. Our recent work has shown that such architectures may be developed not only for terabit-scale memories and naturally defect-tolerant mixed-signal neuromorphic networks, but (rather unexpectedly) also for FPGA-style digital Boolean circuits. [1] For details, see http://rsfq1.physics.sunysb.edu/$\sim $likharev/nano/Springer04.pdf [Preview Abstract] |
Monday, March 21, 2005 9:24AM - 9:36AM |
A14.00004: Simple, High Yield Nano-device Fabrication via SWNT Controlled Growth from a Catalytic Block Copolymer Sarah Lastella, Yung Joon Jung, P.M. Ajayan, Chang Y. Ryu, Dave Rider, Ian Manners, Govind Mallick, Shashi Karna We report a simple process in which single walled carbon nanotubes (SWNT) are grown specifically to allow for a three step device fabrication. Our extremely pure SWNT bundles (dia. 2-5 nm, length $\sim $10 $\mu$m) were produced via a chemical vapor deposition method where a ferrocene containing block copolymer was utilized as the catalyst. Unlike other methods, the nanotube surface coverage density was manipulated via the polymer film thickness to create approximately three to six tubes per 100 $\mu$m$^{2}$. This allows for the direct deposition of metal electrodes onto the silica/nanotube surface without tedious positioning of the nanotubes between metal contacts as an additional processing step. Thus, over 100 working nanodevices can be constructed on a single 1"x1" wafer with this simple three step process: 1) spin casting catalytic polymer film; 2) CVD; 3) metal electrode deposition. I-V measurements show large current flow between gold electrodes ranging from hundreds of $\mu$A to a few mA as a result of the large number of bridging nanotubes. Ease of construction and high device yield make this process a promising candidate for applications as nano-chemical and biological sensors. [Preview Abstract] |
Monday, March 21, 2005 9:36AM - 9:48AM |
A14.00005: A nanodot lattice with molecular interconnects providing reconfigurable logic Carl Onnheim, Jonas Skoldberg, Goran Wendin Using circuit models we investigate a FCC lattice of nanodots, interconnected by molecules with voltage- switchable linear as well as non-linear conductances, deposited on a lithographically defined set of contacts. By applying voltages to these contacts the switchable molecules open conductive paths. We open these according to a target circuit scheme that is able to implement a large set of logic gates, including half-adders. The target circuit in the nanodot lattice consists of an analogue summation node connected to a bistable latch via an NDR connection. The summation node weighs the input, driving and ground voltages. The NDR connection and the bistable latch together converts the analogue voltages to a logical one if in a mid-region and zero if low or high.We have also designed a lithographic context including clocks and transistors such that we can interconnect logic gates to e.g. implement the N-bit adder described by Tour et al. (1). C Husband, S Husband, et al. (2003). ``Logic and memory with nanocell circuits." IEEE Transactions on Electron Devices 50(9): 1865-1875. [Preview Abstract] |
Monday, March 21, 2005 9:48AM - 10:00AM |
A14.00006: The Quantum Interference Transistor David Cardamone, Charles Stafford, Sumit Mazumdar We propose a new class of molecular transistor based on quantum interference. This new type of transistor is smaller than most proposed molecular transistors, yet possesses the important characteristics of traditional macroscopic devices. The proposed device has a broad, step-like I-V characteristic and amplifies current in a controllable way. Numerical calculations making use of the non-equilibrium Green function technique and Landauer-B\"uttiker formalism illustrate this. [Preview Abstract] |
Monday, March 21, 2005 10:00AM - 10:12AM |
A14.00007: Kondo Effect in Bare Electromigrated Break Junctions Andrew Houck, Jarek Labaziewicz, Emily Chan, Joshua Folk, Isaac Chuang Electromigrated break junctions are one of only a very few systems currently available that provide sub-nanometer electrode gaps in a gated geometry. They have been used in several experiments over the past few years to measure transport through nanometer-scale objects such as single molecules. Our measurements show that the electromigrated electrode system--even by itself, without added nanoparticles-- is richer than previously thought. This talk will present gate- dependent transport measurements of Kondo impurities in bare gold break junctions, generated with high yield using an electromigration process that is actively controlled. An unexpected behavior of the splitting is observed in the crossover regime, where spin splitting is of the same order as the Kondo temperature. The Kondo resonances observed here may be due to atomic-scale metallic grains formed during electromigration. [Preview Abstract] |
Monday, March 21, 2005 10:12AM - 10:24AM |
A14.00008: Analysis of Nanocluster-Based Single-Electron Transistors Mario Ancona, Ronald Rendell The possibility of making single-electron transistors (SETs) out of ultra-small metal nanoclusters is intriguing because of the potential for room temperature switching in structures that are 3-5nm in size. In this work the electrical properties that could be expected from such nanocluster-based SETs are explored using numerical simulation. The I-V characteristics are computed using the orthodox theory of Coulomb blockade with only one-electron processes considered and with the capacitances and tunneling resistances of the particular cluster configurations obtained by numerical simulations. These latter calculations must be performed in three dimensions because of the ultra-small radii of curvature involved. Of most interest is an examination of the effect of various structural imperfections on the I-V characteristics since this, in effect, sets the assembly tolerances that would have to be met for a viable nanocluster-based SET technology. [Preview Abstract] |
Monday, March 21, 2005 10:24AM - 10:36AM |
A14.00009: Water Soluble Conducting Polymer Field Effect Transistor for Sensor Application Swanand Vaidya, G.S. Khara, Jaewu Choi We studied the water soluble polythiophene based conducting polymer field effect transistor for chemical and biosensors at nanoscale. Sodium poly [2-3(thienyl) ethoxy-4-butylsulphonate)] (SPBS) is a water soluble polymer. Electrical transport property as a function of gate voltage was investigated using a home-built nanomanipulator with four nanoprobes, which is connected to a picoammeter and an impedance analyzer. In conjunction with this, we studied molecular and electronic structures by a scanning tunneling microscope. The interface between electrodes and polymer play an important role in the charge transport properties. [Preview Abstract] |
Monday, March 21, 2005 10:36AM - 10:48AM |
A14.00010: Molecular Dynamics Simulation of Hybridization Kinetics of Surface-Grafted DNA Naida Lacevic, Arup Chakraborty Increasing interest in development of biosensors results in a need to understand all levels of design and operation of these devices. We focus on a DNA biosensor that is based on molecular recognition between nucleic acids and the subsequent hybridization process. In order to effectively design such a biosensor, it is necessary to understand the effects of grafting density and sequence mismatch on hybridization efficiency. These are of direct relevance to device performance as hybridization efficiency and density determine the signal strength. We use molecular dynamics (MD) simulations to elucidate effects of grafting density on hybridization efficiency and hybridization density as well as the effects of sequence mismatches on hybridization in surface-grafted DNA. We have developed a ``minimal'' coarse-grained model of DNA suitable for long timescale molecular dynamics simulation. We have calculated the hybridization efficiency and conformational order parameter Q$_{\alpha \beta } $(\textbf{r, r'}) between target and probe DNA from MD trajectories. We find that the hybridization efficiency decreases with increase of grafting density, as seen in experiments. We also find that target DNA binding to multiple probes is a dominant effect at higher grafting densities and represents a major obstacle to efficient hybridization efficiency. We show that the width and amplitude of Q$_{\alpha \beta }$(\textbf{r, r'}) are sensitive to the grafting density and number mismatches on the target, respectively. [Preview Abstract] |
Monday, March 21, 2005 10:48AM - 11:00AM |
A14.00011: An Optical Biosensor for Bacillus Cereus Spore Detection Chengquan Li, Harry W. K. Tom We demonstrate a new transduction scheme for optical biosensing. Bacillus cereus is a pathogen that may be found in food and dairy products and is able to produce toxins and cause food poisoning. It is related to Bacillus anthracis (anthrax). A CCD array covered with micro-structured glass coverslip is used to detect the optical resonant shift due to the binding of the antigen (bacillus cereus spore) to the antibody (polyclonal antibody). This novel optical biosensor scheme has the potential for detecting 10$\sim $100 bioagents in a single device as well as the potential to test for antigens with multiple antibody tests to avoid ``false positives.'' [Preview Abstract] |
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