Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session W35: Focus Session: Nanotechnology II |
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Sponsoring Units: FIAP Chair: Curt Richter, National Institute of Standards and Technology Room: Morial Convention Center 227 |
Thursday, March 13, 2008 2:30PM - 3:06PM |
W35.00001: TEBAL: Nanosculpting devices with electrons in a transmission electron microscope Invited Speaker: Manipulation of matter on the scale of atoms and molecules is an essential part of realizing the potential that nanotechnology has to offer. In this talk I will describe transmission electron beam ablation lithography (TEBAL), a method for fabricating nanostructures and fully integrated devices on silicon nitride membranes by nanosculpting evaporated metal films with electron beams. TEBAL works by controllably exposing materials to an intense and highly focused beam of 200 keV electrons inside the transmission electron microscope (TEM). The effect of electron irradiation can be used to controllably displace or ablate regions of the metal with resolution on the scale of tens of atoms per exposure. In situ TEM imaging of the ablation action with atomic resolution allows for real-time feedback control during fabrication. Specific examples presented here include the fabrication and characterization of nanogaps, nanorings, nanowires with tailored shapes and curvatures, and multi-terminal devices with nanoislands or nanopores between the terminals. These nanostructures are fabricated at precise locations on a chip and seamlessly integrated into large-scale circuitry. I will discuss how the combination of high resolution, geometrical control and yield make TEBAL attractive for many applications including nanoelectronics, superconductivity, nanofluidics and molecular (DNA) translocation studies through nanopore-based transistors. References: 1) M.D. Fischbein and M. Drndic, ``Sub-10 nm Device Fabrication in a Transmission Electron Microscope'', Nano Letters, 7 (5), 1329, 2007. 2) M. D. Fischbein and M. Drndic, ``Nanogaps by direct lithography for high-resolution imaging and electronic characterization of nanostructures'', Applied Physics Letters, 88 (6), 063116, 2006. [Preview Abstract] |
Thursday, March 13, 2008 3:06PM - 3:18PM |
W35.00002: Atomic Precision in Nano-Electronics Douglas Strachan, Danvers Johnston, Beth Guiton, Ye Lu, Sujit Datta, Peter Davies, Dawn Bonnell, Charlie Johnson One of the greatest challenges in developing molecular-scale devices is to fabricate and monitor their formation with atomic precision. Recently, we have developed an electromigration technique that employs feedback for controllably electromigrating a nano-scale electrode with atomic precision at room temperature [1]. We will discuss our recent progress advancing this technique towards atomically precise nano-electronics. This will include in-situ transmission electron microscopy which shows evidence for highly crystalline electrode formation and the parallel fabrication of nanogaps for scaling-up to very large-scale integrated-circuits. Our results have implications on the development of a wide range of novel molecular-scale devices. Funding provided by: NSF-NSEC/NBIC DMR-0425780, NSF-NIRT Grant No. 0304531, and MRSEC award No. DMR05-20020. [1] D. R. Strachan, et al., Appl. Phys. Lett. 86, 043109 (2005). [Preview Abstract] |
Thursday, March 13, 2008 3:18PM - 3:30PM |
W35.00003: Quantifying the properties of nano-composites. Murray Daw, Bo Zhang, Jian He, Terry Tritt With the proliferation of nano-composites produced for possible thermoelectric application, we ask the question: To what extent is a given nano-composite like other composites? Or, in other words, when do we know that we have something new? To address this we apply the classical theory of composites to specific nano-composites grown and characterized at Clemson. The theory is very simple and assumes explicitly very simple properties of the materials, the most important being Fourier's Law/Ohm's Law. Given this assumption, the theory of composites can be applied to the nano-composites based on what is known of the microstructure. This ``classical'' result then forms the basis by which the properties can be compared to determine if non-classical effects are being observed. One simple theory is the application of rigorous bounds, such as the Hashin-Strikman Bounds which are based only on very simple microstructural descriptors. Another simple theory is the application of FEM, which can be constructed directly from SEM images of the samples using the NIST code ``OOF''. The FEM produces specific predictions for the composite properties. We find that the Hashin-Strikman Bounds are very useful for analyzing the thermal conductivities of composites, but are too loose to be useful for low-temperature electrical conductivity of composites composed of metals and insulators, where the FEM technique can be applied successfully. [Preview Abstract] |
Thursday, March 13, 2008 3:30PM - 3:42PM |
W35.00004: `Focused Assembly' of V$_{2}$O$_{5}$ Nanowires for Fabrication of Metallic Nanowire Sensors Tae Hyun Kim, Sung Myung, Kwang Heo, Seunghun Hong We present a method named `focused assembly' for high-precision assembly of pristine V$_{2}$O$_{5}$ nanowires (NWs) on solid substrates. In this method, 'microscale' self-assembled monolayer patterns with 'gradient' surface molecular density `focused' the assembly of V$_{2}$O$_{5}$ NWs onto the `nanoscale' regions on a metallic thin film just like a lens focuses the light. The assembled NWs could be utilized as a shadow mask during the ion-milling process to generate metallic NW-based devices. As a proof of concepts, we successfully demonstrated the fabrication of metallic NW-based sensors to detect thiol molecules or hydrogen gas under ambient conditions. This focused assembly phenomenon gives us new insights about the directed assembly process of nanostructures. Furthermore, this approach provides us an easy, but efficient, means to mass-produce NW-based devices for various practical applications such as field effect transistors, chemical sensors and nanoscale interconnectors. [Preview Abstract] |
Thursday, March 13, 2008 3:42PM - 3:54PM |
W35.00005: Nanomechanical Spectroscopy: A novel route to label-free chemical sensing Peter Greaney, Jeffrey Grossman We propose a novel spectroscopic technique in which the vibrational modes of an analyte molecule are probed directly using a nanoscale mechanical resonator. It is anticipated that such ``nanomechanical spectroscopy'' can provide a method for label free chemical sensing. We elucidate the concept of the nanomechnical spectroscope with the example of using an array of carbon nanotubes to detect a series of simple test molecules. In these examples, energy is transferred between the molecular vibrations of the analyte and specific phonon modes of the carbon nanotubes. Molecular dynamics simulations are used to explore the feasibility of this energy exchange for chemical sensing, and limits of both sensitivity and selectivity. [Preview Abstract] |
Thursday, March 13, 2008 3:54PM - 4:06PM |
W35.00006: `Lens' Effect in Directed Assembly of Nanowires on Gradient Molecular Patterns Moon Gyu Sung, Sung Myung, Jiwoon Im, Seunghun Hong We report a new phenomenon, named here as the \textit{`lens'} effect, in the directed-assembly process of nanowires (NWs) on self-assembled monolayer (SAM) patterns. In this process, the adsorption of NWs is focused in the nanoscale regions at the center of microscale SAM patterns with gradient surface molecular density just like an optical lens focuses light. As a proof of concepts, we successfully demonstrated the massive assembly of V$_{2}$O$_{5}$ NWs and single-walled carbon nanotubes (swCNTs) with a nanoscale resolution using only microscale molecular patterning methods. This work provides us with important insights about the directed-assembly process, and from a practical point of view, it allows us to generate nanoscale patterns of NWs over a large area for mass fabrication of NW-based devices. [Preview Abstract] |
Thursday, March 13, 2008 4:06PM - 4:18PM |
W35.00007: In$_{2}$O$_{3}$ Nanoparticles for Gas Sensors Zengxing Zhang, Daniela Caruntu, Charles J. O'Connor, Weilie Zhou In the last decades, sensors based on nanostructured materials have attracted much attention. Generally, nanosensors often demonstrate excellent sensitivities because of their high specific surface area and comparable size to the detected targets (chemicals or biomolecules). So far, lots of efforts have been put on the fabrication of nanowires based nanosensors. In this talk, we reported our recent work on employing wet-chemically synthesized indium oxide (In$_{2}$O$_{3})$ nanoparticles for gas sensing. The nanoparticles were self-assembled between the gold electrodes patterned on silicon substrates covered with thermal oxide film using e-beam nanolithography. Several gases, such as ammonia (NH$_{3})$, hydrogen sulfide (H$_{2}$S), etc., were used for the testing. The results exhibit that the sensitivity can be reached down to PPM order. In addition, the sensitivity in terms of nanoparticle size, temperature, etc, were also investigated. [Preview Abstract] |
Thursday, March 13, 2008 4:18PM - 4:30PM |
W35.00008: Environment of TiO$_{2 }$ nanoparticles as an important factor to achieve highly efficiency on dye sensitized solar cells Tereza Paronyan, M.C. Lin Amorphous TiO2 nanoparticles were synthesized by sol gel technique. Environment of nanoparticles was neutralized by ammonia, and pH5.8 of TiO2 gel was achieved in result, which is close to the point of zero charge (PZC) of anatase TiO2. Highly interconnected, mesoporous, transparent films were fabricated from the TiO2 colloid with pH5.8. AFM, SEM XRD analyses were carried out for the investigation the size of nanoparticles, the surface morphology and the crystal structure of films. Volt-amperic characteristics showed an improvement in the cell efficiency along with the increasing of pH TiO2 colloid. The cells parameters (Voc, FF, Jsc, $\eta )$ were studied depending on the pH of TiO2 colloid. Increasing pH of the colloid from 2.1 to 5.8 enhanced the overall conversion efficiency of the dye-sensitized solar cells by approximately 30{\%} , and 9.2 {\%} of efficiency was achieved with N719 dye under illumination by simulated AM1.5 solar light (100 mW/cm-2). [Preview Abstract] |
Thursday, March 13, 2008 4:30PM - 4:42PM |
W35.00009: Electron Thermal Microscopy of Multiwalled Carbon Nanotubes Kamal Baloch, Todd Brintlinger, John Cumings A thorough electrical and thermal characterization of carbon nanotubes (CNTs) is essential for their application as electrical and thermal devices. We demonstrate high-resolution thermal imaging of multiwall CNT using electron thermal microscopy. This is achieved by observing the solid to liquid phase transition of low melting point indium islands in a transmission electron microscope. High resolution thermal maps thus obtained provide a qualitative analysis of transfer of heat along a CNT suggesting a trend of CNT acting as a heat spreader. Also, important parameters like thermal conductivity of the CNT can be extracted by finite element modeling. The temperatures involved are $\sim $200C and the samples can be operated over several voltage cycles. Experimental technique, high resolution maps, real time videos, and simulation results will be presented. [Preview Abstract] |
Thursday, March 13, 2008 4:42PM - 4:54PM |
W35.00010: The Nuclear Environment for Electron Spins in a Double Quantum Dot David Reilly, Jacob Taylor, Jason Petta, Charles Marcus, Micah Hanson, Art Gossard We report measurements examining the nuclear spin environment for electrons in a GaAs double quantum dot. The hyperfine field, which drives transitions of a two-electron spin state, is detected via spin-to-charge transfer and rf-QPC readout. Fluctuations of the hyperfine field are measured to be broadband, with spectral content ranging from milliseconds to the decorrelation time of $\sim$ 10 seconds. In addition, we demonstrate dynamic nuclear polarization (DNP) using a cyclic gate-pulse sequence. Relaxation of the DNP is studied using time-resolved measurements and found to be sensitive to the spin-state of electrons. The presence of a small DNP is found to suppress hyperfine fluctuations by a factor of $\sim$ 100, leading to a time-ensemble dephasing time, $T_2^*\sim$ 1 microsecond for electron spins. [Preview Abstract] |
Thursday, March 13, 2008 4:54PM - 5:06PM |
W35.00011: Nanoscale probing of material properties across antiparallel domain wall in ferroelectrics Vasudeva Rao Aravind, Lili Tian, Nozomi Odagawa, Samrat Choudhury, Pavel Capek, Volkmar Dierolf, Anna N. Morozovska, Eugene A. Eliseev, Long-qing Chen, Yasuo Cho, Sergei Kalinin, Venkatraman Gopalan Although the intrinsic width of an ideal antiparallel ferroelectric domain wall is expected to be step-like on a unit cell level ($\sim $0.5nm), we have recently shown that actual widths of these walls can extend to $\sim $20-100nm in lithium niobate and lithium tantalate (L.Tian \textit{et al}., Physical Review Letters (\textit{in review})). In this work we study the variation of material properties coercive field and switchable ferroelectric polarization as a function of the distance from the domain wall in lithium niobate. Until recently, the study of these material properties on the nanoscale were limited by the lack of theoretical modeling of the instrument resolution limits. Using experimental results and theoretical modeling we demonstrate the relation between intrinsic width of the domain wall and its effect on material properties. [Preview Abstract] |
Thursday, March 13, 2008 5:06PM - 5:18PM |
W35.00012: Electrostatic and Nanotechnology – Multidisciplinary Approach - for Space Radiation Shielding Ram Tripathi, John Wilson, Robert Youngquist For the success of NASA's new vision for space exploration to Moon, Mars and beyond, exposures from the hazards of severe space radiation in deep space long duration missions is ``a must solve'' problem. The exploration beyond low Earth orbit to enable routine access of space will require protection from the hazards of the accumulated exposures of space radiation. There is a need to look to new horizons for newer technologies. The present multidisciplinary investigation explores the feasibility of using the active electrostatic shielding in concert with the state-of-the-art materials shielding and protection technologies. The full space radiation environment has been used, for the first time, to explore the feasibility of multidisciplinary shielding. The goal is to repel enough positive charge ions so that they miss the spacecraft without attracting thermal electrons and further attenuate the exposure using nano-materials. Conclusions are drawn for the future directions of space radiation protection. [Preview Abstract] |
Thursday, March 13, 2008 5:18PM - 5:30PM |
W35.00013: Probing Local Structures in ZrO$_{2}$ Nanocrystals Using EXAFS Y.L. Soo, P.J. Chen, S.H. Huang, T.J. Shiu, T.Y. Tsai, Y.H. Chow, Y.C. Lin, S.C. Weng, S.L. Chang, J.F. Lee, C.L. Cheung, R.F. Sabirianov, F. Namavar, W.N. Mei Extended x-ray absorption fine structure (EXAFS) has been employed to investigate the local structures surrounding Zr in cubic zirconia thin films prepared by an ion beam assisted deposition technique. These materials have demonstrated promising mechanical properties such as improved hardness and lubricant wettability compared to yttria-stabilized zirconia. To verify the cubic structure of zirconia in films prepared under different growth conditions and to fully understand the mechanism leading to their unique physical properties, the structural information is a required prerequisite. Since zirconia is in the form of nanosized crystallets, conventional x-ray diffraction method is not useful for this purpose. Our x-ray results reveal cubic-like structure with O vacancies around Zr in several nanocrystal samples. Powders of cubic zirconia prepared using chemical methods were also measured for comparison. [Preview Abstract] |
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