Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session D27: Advances in Instrumentation and Measurement I |
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Sponsoring Units: GIMS Chair: Larry Rubin, MIT Room: 329 |
Monday, March 16, 2009 2:30PM - 2:42PM |
D27.00001: Mechanical properties of silicon nanowires studied by polarization-enhanced fiber-optic interferometry John Nichol, Eric Hemesath, Lincoln Lauhon, Raffi Budakian Silicon nanowires have recently attracted attention as promising force sensors due to their inherent low dissipation and high frequency. One of the principal challenges to the use of nanowires as scanning probe force sensors is displacement detection. By exploiting the polarization anisotropy in light scattering from single nanowires, we have used fiber-optic interferometry to detect the displacement of individual silicon nanowires. We achieve a displacement sensitivity of 0.5~pm/$\surd $Hz for 15~$\mu $W of light incident on the nanowire. The nanowires studied have ultralow mechanical dissipation in the range of 2$\times $10$^{-15}$-~2$\times $10$^{-14}$~kg/s. We also discuss the effects of hydrogen surface passivation on mechanical dissipation. Further progress toward the use of nanowires as scanning probe force sensors is discussed. [Preview Abstract] |
Monday, March 16, 2009 2:42PM - 2:54PM |
D27.00002: Zero Flux Anomaly in Mesoscopic Normal Metals Julie Bert, Hendrik Bluhm, Nicholas Koshnick, Martin Huber, Kathryn Moler Our recent scanning SQUID susceptometry measurements of individual mesoscopic normal metal rings found persistent currents consistent with theoretical predictions. In addition to the persistent current signal, all rings exhibited a step anomaly in the SQUID response vs flux around zero applied flux and a large paramagnetic linear susceptibility. We present the characteristics of the zero flux anomaly observed in multiple rings and thin films and explore possible explanations. Key features include a notable frequency dependence between 11 and 333 Hz and a strong spatial correlation with the large paramagnetic spin signal. [Preview Abstract] |
Monday, March 16, 2009 2:54PM - 3:06PM |
D27.00003: Second Harmonic Technique for Thermal Conductivity Measurement in a Pulsed Magnetic Field Yoko Suzuki, Jonathan B. Betts, Albert Migliori We describe a second-harmonic technique to be used eventually to probe the thermal conductivity of LSCO with superconductivity suppressed by high magnetic fields. The technique is suitable for the high-noise environment of pulsed magnets. Unlike the 3$\omega $ technique, a heater and a thermometer are mounted separately. Therefore, the 2$\omega $ signal is the dominant signal in the thermometer output. The frequencies are chosen so that the thermal penetration depth is smaller than the sample thickness. The thermometer response time and thermal impedance associated with material interfaces are carefully tested and compared to calculation. The calculations are based on exact solutions of the full bulk heat transport equations and produce results different from the lumped-constant approximations often used in ac calorimetry. Work performed under the auspices of the National High Magnetic Field Laboratory. [Preview Abstract] |
Monday, March 16, 2009 3:06PM - 3:18PM |
D27.00004: Nanoscale imaging magnetometry with single spins in diamond Gopalakrishnan Balasubramanian, Julia Tisler, Roman Kolesov, Fedor Jelezko, Joerg Wrachtrup Single Nitrogen-Vacancy colour centers in diamond are gaining popularity because of its exceptional optical and spin properties. The single spin of the defect can be manipulated optically, providing a efficient way to entangle single electron spins and couple nuclear spins qubits in diamond.[1] Long spin coherence time of these single defects finds application as sensitive magnetic field probes. Using engineered diamond we can achieve ultrahigh sensitivity using which we will be able to detect a single external electron or nucelar spin.[2] Controlled creation of these color centers inside nanodiamonds offers diverse applications. By attaching these single spins to the tip of a scanning probe, we were able to perform sensitive scanning probe magnetometry at nanoscale.[3] Improving this device by using quantum grade diamond and synchronized NMR pulse sequences we would have the ability to perform nanoscale NMR/MRI of single molecules.\\[0pt] [1] Neumann, P. et al. Multipartite Entanglement Among Single Spins in Diamond. Science 320, 1326-1329 (2008).\\[0pt] [2] Maze, J. R. et al. Nanoscale magnetic sensing with an individual electronic spin in diamond. Nature 455, 644-647(2008).\\[0pt] [3] Balasubramanian, G. et al. Nanoscale imaging magnetometry with diamond spins under ambient conditions. Nature 455, 648-651(2008). [Preview Abstract] |
Monday, March 16, 2009 3:18PM - 3:30PM |
D27.00005: Elastic cotunneling through a quantum dot in the presence of electromagnetic fluctuations Vladimir Bubanja We consider the effect of electromagnetic fluctuations on electron transport through a quantum dot in the Coulomb blockade regime. We obtain the analytic expression for the elastic cotunneling current which shows that the electromagnetic fluctuations cause the power law suppression at low voltages, $I \sim V^{1+2 R/R_{K}}$ where $R$ is the Ohmic part of the circuit impedance and $R_{K}$ is the quantum resistance. This elastic cotunneling current is proportional to the level spacing of the dot and is the dominant transport below certain cross-over voltage, above which inelastic cotunneling dominates. Both cotunneling processes are of importance in accuracy considerations of the operation of the R- pump, which is a single-electron tunneling device that is of interest for applications in electrical metrology. [Preview Abstract] |
Monday, March 16, 2009 3:30PM - 3:42PM |
D27.00006: Graphenated Infrared Screens: A New Platform for Bio- Detection. Amrita Banerjee, Dieter Moeller, Haim Grebel We are proposing a novel spectroscopic tool -- the graphenated infrared (IR) screens. It is aimed to enhance weak IR and Raman signals. Metallo-dielectric screens have been used for astronomy and remote sensing applications. These periodic structures are at resonance with the IR wavelength of interest: a standing wave of surface charges is formed at resonance conditions, which enables transmission or, reflection of certain IR bands. Graphene is a monolayer thick crystal of carbon. It is chemically inert and exhibits very large mobility values. Recently, we succeeded in fabricating mono and a few-layered suspended graphene on top of these IR screens. The result is a new spectroscopic platform, which enhances weak IR and Raman signals of molecules and specifically, bio-species, which are residing on the graphene layer. The IR absorption and Raman signals of bio-species under test have exhibited strong dependence on the screen periodicity pitch as well as on its orientation. [Preview Abstract] |
Monday, March 16, 2009 3:42PM - 3:54PM |
D27.00007: Development of a Microfocus Beamline for Angle-Resolved Photoelectron Spectroscopy T. Miller, M. Bissen, T.-C. Chiang Synchrotron-based angle-resolved photoemission spectroscopy has proven to be a powerful tool in the elucidation of electronic structure of solids. The technique is now being applied to a wide variety of materials, and the macroscopic sampling area has become a limitation. For example, cleaving may expose different crystal planes, and the area covered by the incident photon beam may then consist of a collection of small domains with different photoemission spectra. The result is an average which obscures the true nature of the material. For this reason a beamline with a small focus has been proposed to be used with an angle-resolved photoemission endstation at the Synchrotron Radiation Center in Stoughton, WI. Reflective optics would be used to produce a microfocus at the sample of the light from an undulator beamline, providing submicron spatial resolution, while electron emission angles and energies are measured using an imaging electron energy analyser. The microfocusing optics and possible applications will be discussed. [Preview Abstract] |
Monday, March 16, 2009 3:54PM - 4:06PM |
D27.00008: Near field emission scanning electron microscopy Taryl Kirk, Lorenzo De Pietro, Olivier Scholder, Thomas Baehler, Urs Ramsperger, Danilo Pescia We present a simple ``near field emission scanning electron microscope'' (NFESEM) capable of imaging conducting surfaces with high spatial resolution. In this instrument electrons are excited from the sample surface after undergoing interactions with a low-voltage ($<$ 60V) primary beam of electrons field-emitted from a Tungsten tip positioned tens of nanometers above the sample. Topographic images, determined from the intensity variations of secondary and backscattered electrons, yield a vertical resolution on an atomic scale and a lateral resolution of less than two nanometers. We report on the first topographic electron intensity images of terraces and mono-atomic steps on a single crystal substrate, not yet attained with a remote electron gun in conventional scanning electron microscopy. The topographic contrast of the extracted electrons and the field emission (FE) current are indistinguishable, in agreement with theoretical models of optimal spatial resolution. We assert that additional analysis of the secondary electrons will also exhibit a comparable resolution. [Preview Abstract] |
Monday, March 16, 2009 4:06PM - 4:18PM |
D27.00009: Particle Characterization using Holographic video Microscopy Foo Chiong Cheong, David Grier In-line holographic video microscopy can be interpreted with Lorenz-Mie theory to obtain exceptionally precise measurements of individual colloidal spheres' dimensions and optical properties, while simultaneously tracking their three dimensional motions with nanometer-scale spatial resolution at video rates. This method works over the entire range of particle sizes and compositions for which Mie scattering theory applies. Unlike other light scattering techniques for measuring particle size or refractive index, holographic particle analysis can be applied directly to individual particles. [Preview Abstract] |
Monday, March 16, 2009 4:18PM - 4:30PM |
D27.00010: Three-dimensional position determination of nanoparticles using a two-photon microscope James Germann, Lloyd Davis, Brian Canfield, Alexander Terekhov We are developing a means to extend the two-photon microscope to enable three-dimensional sub-diffraction measurement of the position and trajectory of a single nanoparticle as it traverses the probe volume. By use of a Ti-Sapphire laser and a double-Mach-Zehnder interferometer configuration, four laser beams with temporally interleaved pulses are created. These are tightly focused by a 1.2-NA water-immersion microscope objective to four overlapping volumes centered at slightly offset points arranged in a tetrahedron. Fluorescence from the four-focus probe volume is then collected onto a single-photon avalanche diode and the photon time stamps are recorded. Time-resolved photon detection with maximum-likelihood analysis is thereby used to determine the position of the nanoparticle from the relative intensities of fluorescence from each of the four foci.~ We present measurements of the profile of the four-focus configuration and results from calibration experiments obtained by translating a single gold nanodot or a fluorescent nanobead through the probe volume. Application of the position determination to single-particle trapping is also briefly discussed. [Preview Abstract] |
Monday, March 16, 2009 4:30PM - 4:42PM |
D27.00011: Capabilities of high-sensitivity spectral fluorescence-lifetime imaging for resolving spectroscopically overlapping species Justin Crawford, Lloyd Davis, Brian Canfield The ability to separate the contributions from spectroscopically overlapping fluorophores has enabled significant breakthroughs in cellular imaging. However, commercial microscopes for this purpose generally use analog light detection with least-squares curve-fitting analysis. Improvements in sensitivity are possible and will lead to new applications. To this end, we have constructed a microscope with a high-throughput Brewster-prism spectrometer and four high-quantum efficiency single-photon detectors, coupled with time-correlated single photon counting electronics to provide added temporal resolution. We have demonstrated the use of maximum-likelihood (ML) methods for analyzing small numbers of photons to find the contributions from fluorescent species with differences in excitation and emission spectra. However, it is difficult to resolve fluorophores with different temporal decay profiles because the single-photon counting modules exhibit a count-rate-dependent time-walk. We discuss extension of the ML-analysis to account for a varying time-walk and results from Monte Carlo simulations to ascertain the minimum number of photons needed to reliably resolve specific fluorophores. [Preview Abstract] |
Monday, March 16, 2009 4:42PM - 4:54PM |
D27.00012: Development of a low-cost small-sized scanning transmission ion microscope of moderate resolution with educational and other potential applications Arthur Pallone Scanning transmission ion microscopy (STIM) has applications in many fields of study such as materials and device engineering, biological and geological sciences, and the arts. Since STIM is practiced at ion beam facilities, many persons outside of the ion beam community who could benefit from STIM are unaware of its potential. In an effort to better educate the public about STIM, an inexpensive portable demonstration unit suitable for interactive classroom use and public outreach events is under development. The required parts are readily available, mostly at local electronics and office supply stores. Progress toward completion of the demonstration unit and future efforts to modify the unit to support thin film research will be discussed. Activities that demonstrate the three modes of STIM will also be presented. [Preview Abstract] |
Monday, March 16, 2009 4:54PM - 5:06PM |
D27.00013: A two dimensional piezoeletric micro-positioner K.-W. Ng, John Nichols, J. W. Brill A scanning probe microscope can provide very high resolution imaging, but only within a small scanning area. There is a high demand for compact long range positioners, so that distant locations on the same sample can be imaged and studied. We will present information on the design and operation of a piezoelectric driven two-dimensional micropositioner that can provide long range motion in the x- and z-directions. The z-direction motion can be used for coarse approach, while the x-direction motion can be used to scan along the sample surface. The device is build as one single unit, so it is extremely compact and rigid, and can provide a high resonance frequency platform for high performance scanning probe microscopy. [Preview Abstract] |
Monday, March 16, 2009 5:06PM - 5:18PM |
D27.00014: High Speed Scanning Property Mapping ($>$1 frame per second) Bryan Huey, Nicholas Polomoff, Atif Rakin, Vincent Palumbo Atomic Force Microscopy is coupled with concepts of acoustics to achieve nanoscale property contrast at line scanning rates approaching several kHz. This allows novel measurements of surface dynamics, efficient large area imaging, and high throughput experiments with SPM. Examples for mechanical contrast on block copolymers, semiconductors, and eutectic alloys are included, as well as high speed electric and magnetic field imaging. Coupled electromechanical contrast (piezoelectric) is also employed with PZT thin films to uniquely monitor ferroelectric domain dynamics. [Preview Abstract] |
Monday, March 16, 2009 5:18PM - 5:30PM |
D27.00015: Method for Detecting Position and Orientation of Convex Objects in 3D Scans Alexander Jaoshvili, Paul Chaikin We have developed an algorithm for detecting the center positions and orientations of mono-disperse objects which pack a container from the data collected in a 3 dimensional scan such as obtained by MRI. The algorithm is applied to a variety of geometrical convex shapes including, ellipsoids, cubes and tetrahedrons. From the positions and orientations we are able to reconstruct the number and type of interparticle contacts and constraints and thus to test Maxwell's Isostatic conjecture in the case of ``random close packing.'' We also obtain translational and orientational correlation functions. [Preview Abstract] |
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