Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session W44: Microscopy: Near-field, X-ray, Optical, and Probe |
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Sponsoring Units: GIMS Chair: Joseph Stroscio, NIST Room: LACC 518 |
Thursday, March 24, 2005 2:30PM - 2:42PM |
W44.00001: A Novel Scanning Near-Field Microwave Microscope Capable of High Resolution Loss Imaging Atif Imtiaz, Steven Anlage To study novel physics in condensed matter and materials science, experimental techniques need to be pushed for better sensitivity and higher spatial resolution. Classical techniques of probing the high frequency electrical properties of materials are limited in resolution to the wavelength of the incident electromagnetic wave. We report here a novel near-field microwave microscope to image materials contrast, with 2.5 nm spatial resolution in capacitance. Our objective is to improve the spatial resolution in local loss imaging. We will present evidence of sheet resistance contrast in a Boron-doped Silicon sample on sub- micron length scales. We will present quantitative analysis of the data on the Boron-doped Silicon sample in light of evanescent wave model of the microscope that we have developed. In addition, the probe to sample interaction on nanometer length scales will be discussed [1]. This work has been supported by an NSF IMR Grant DMR-9802756, and the University of Maryland/Rutgers NSF-MRSEC through the Near Field Microwave Microscope Shared Experimental Facility Grant DMR-00-80008. [1] Atif Imtiaz, Marc Pollak, Steven M. Anlage, John D. Barry and John Melngailis, ``\textit{Near-Field Microwave Microscopy on nanometer length scales}'', to be published in J. Appl. Phys. (Feb. 1, 2005). [Preview Abstract] |
Thursday, March 24, 2005 2:42PM - 2:54PM |
W44.00002: SNOM investigation of the electromagnetic field intensity and polarization distribution in the vicinity of nanostructures Dmitriy Muzychenko, Mihail Bashevoy, Alexandr Ejov, Sergey Magnitskiy, Dmitriy Malakhov, Vladimir Panov, Jarkin Toursinov Experimental and calculated results of the investigation of the electromagnetic field distribution including its polarization characteristics in the vicinity of the surface submicro- and nanostructures are presented. Experimental investigation was realized by aperture type scanning near-field optical microscopes (SNOM), which provided both high spatial resolution and large scanning range. Shear-force detection was used for the control of aperture to surface gap. Normal resolution better than 0.1 nm was demonstrated for this gap control system. Collection mode was used for electromagnetic field distribution observation. Theoretical computation was realized by finite-difference time-domain (FDTD) method. Experimental 3D maps of intensity and polarization distribution as result of diffraction of light at sub-wavelength aperture in metal screen, dielectric and metallized nanocylinders were obtained. The qualitative difference between the orthogonal polarized components distribution near sub-wavelength aperture in aluminium screen was experimentally shown. The electromagnetic field concentration in the proximity of the dielectric nanocylinders was observed. This observation gives good fit with the results of FDTD computations. Spiral type electromagnetic field distribution pattern was experimentally observed in the proximity of metallized nanocylinders, which is unexpected from both experimental and theoretical points of view. [Preview Abstract] |
Thursday, March 24, 2005 2:54PM - 3:06PM |
W44.00003: Dual coherent frequency-comb infrared spectrometer Fritz Keilmann We demonstrate a new concept of broadband Fourier-transform infrared spectroscopy (FTIR) based on a multi-heterodyne detection principle. Two coherent mid-infrared beams that contain slightly offset harmonic frequency combs are superimposed on a photoconductive detector. The signal contains a radio-frequency harmonic spectrum that replicates the mid-infrared spectrum. The latter can be retrieved by recording the detector signal \textit{vs} time (much as an interferogram known in FTIR) and subsequent Fourier transformation. In our experiment, two 10 fs Ti:sapphire lasers separately generate two mid-infrared beams by difference-mixing in GaSe. The effective radio frequency is chosen by slightly offsetting the pulse repetition rates. We demonstrate an interferogram acquisition duration as short as 1 $\mu $s which could be interesting for taking ``snapshot'' infrared spectra of single transient events such as in high-field magnetospectroscopy or in chemical reactions. We intend to exploit the advantage of the diffraction-limited focusability of this spectrometer for mid-infrared microscopy and for scattering-type near-field microscopy. -- F. Keilmann, C. Gohle, and R. Holzwarth, Opt. Lett. \textbf{29}, 1542 (2004) [Preview Abstract] |
Thursday, March 24, 2005 3:06PM - 3:18PM |
W44.00004: Lensless Holographic X-ray Imaging of Magnetic Nanostructures William Schlotter, J. Luning, J. Stohr, S. Eisebitt, M. Lorgen, W. Eberhardt, O. Hellwig Applying soft x-rays to Fourier transform holography, we have imaged a magnetic nanostructure with 50 nm resolution. The key element is an x-ray opaque mask containing two apertures which are 1.0$\mu $m and 100nm in diameter. By integrating the magnetic sample film to the mask structure, the larger aperture defines the field of view, and the smaller aperture transmits a holographic reference beam. Illumination with coherent soft x-rays produces an interference hologram in the far field which is recorded with a CCD detector. A single spatial Fourier transform of the hologram yields an image of the magnetic domain structure. This truly lensless full field imaging technique is ideally suited for ultrafast imaging with a single x-ray pulse from the now imminent x-ray lasers. [Preview Abstract] |
Thursday, March 24, 2005 3:18PM - 3:30PM |
W44.00005: Wide field imaging of nanosize (1D or 2D) objects Marie-Pierre Valignat, Dominique Ausserre We present a new technique that increases the sensitivity of present optical microscopy by two order of magnitude without reducing it lateral resolution. The technique is based on the association of specific surfaces as sample supports and microscope observation between cross polarizers. It is particularly efficient when the microscope is turned into DIC mode. In this way, one can visualize ultra-thin film (0.7 nm) and isolated wire-like object of nanometer size diameter (nanotube, combed DNA). It can operate in air or in immersion and should be of great value in the studies of biological structures. [Preview Abstract] |
Thursday, March 24, 2005 3:30PM - 3:42PM |
W44.00006: High-resolution scanning hall probe microscopy C.W. Hicks, M.A. Topinka, J.H. Bluhm, K.A. Moler, J.W. Guikema, E. Zeldov, H. Shtrikman Scanning hall sensors can be used to directly image magnetic fields at surfaces. They offer high resolution, high sensitivity, operability from cryogenic to room temperature, and linearity. We have fabricated hall sensors on GaAs / Al$_{0.35}$Ga$_{0.65}$As and GaAs / Al$_{0.3}$Ga$_{0.7}$As heterostructures, one containing a 2D electron gas 40 nanometers below the surface and another 140nm below the surface, as well as an In$_{0.5}$Al$_{0.5}$As / GaSb / AlSb / InAs heterostructure containing a 2DEG 21nm below the surface. The sensitive areas of our probes range from microns to 60nm on a side. We report on the field sensitivities of the probes and their spatial resolution in a scanning configuration. [Preview Abstract] |
Thursday, March 24, 2005 3:42PM - 3:54PM |
W44.00007: Design and Construction of a UHV-LT-STM System for Atom Manipulation on MBE Grown Surfaces Danda-P. Acharya, Kendal Clark, Thy Vo, Joel Vaughn, Saw-Wai Hla An ultra-high-vacuum low--temperature scanning-tunneling-microscope (UHV-LT-STM) capable of single atom/molecule manipulation on molecular beam epitaxy (MBE) grown samples has been design and constructed. The STM scanner design is based on a modified Besoke-Beetle type and the thermal drift of the system is less than 0.1 nm/hr, which allows to conduct I-V, dI/dV and vibrational tunneling spectroscopy measurements at single atom level. The freshly grown MBE samples from a separate UHV system can be transferred into our LT-STM system via a portable UHV chamber without exposing the samples to the air. This allows the atom manipulation and STM spectroscopy experiments to be performed on specially tailored surfaces. As demonstrations, single atom manipulation and spectroscopy measurements conducted on Ag(111) and GaN (0001) surfaces at 4.8 K will be presented. This work is financially supported by the NSF-NIRT grant no. DMR- 0304314. [Preview Abstract] |
Thursday, March 24, 2005 3:54PM - 4:06PM |
W44.00008: Development of low temperature scanning probe microscope Yongho Seo, Paul Cadden-Zimansky, Venkat Chandrasekhar We have built a low temperature scanning probe microscope using a quartz crystal tuning fork. This microscope can be used for STM, AFM, EFM, and MFM at temperatures ranging from room temperature to millikelvin temperatures. The tuning fork, a self- actuating and self-sensing sensor, has a 32 kHz resonance frequency, 10$^5$ quality factor, and 1300 N/m spring constant. Due to the small vibration ($\sim$ 0.1 nm) of the tuning fork, it is an ideal tool for ultra-high resolution imaging. Also, the tuning fork is particularly suited for millikevin temperature range SPM due to its low dissipation power ($\sim$ 1 pW). We present low temperature EFM images of boron nano wires, low temperature MFM images of magnetic dot arrays embedded in a superconducting matrix, and high resolution topographic and EFM images of carbon nanotubes. [Preview Abstract] |
Thursday, March 24, 2005 4:06PM - 4:18PM |
W44.00009: Realization of a sub-Kelvin ultra-high vacuum scanning tunneling microscope in high magnetic field Xi Chen, Ungdon Ham, Chi Chen, Wilson Ho A sub-Kelvin ultra-high vacuum (UHV) scanning tunneling microscope (STM) in high magnetic field has been designed and developed. The Besocke type scanner is modified to meet the requirements of sub-Kelvin temperature and high magnetic field. The scanner is mounted to the He3 pot of a bottom loading UHV compatible helium- 3 cryostat with a 9 Tesla superconducting magnet. The bottom loading design substantially reduces the distance between experimental and access positions where STM tips and samples can be exchanged without breaking UHV. The helium-3 insert remains at low temperature during tip and sample exchange. The helium-4 reservoirs for the non-bakeable NbTi superconducting magnet and the UHV space are thermally separated in order to achieve UHV condition without overheating the magnet. Two layers of aluminum shields make use of the enthalpy of the cold He4 vapor for radiation shielding without liquid nitrogen. A two-chamber UHV system creates reliable environment for tip and sample preparation, and surface imaging and characterization. Various atoms and molecules can be deposited at room or low temperatures. The STM system has the unique capability to probe matter at very low temperatures, in high magnetic fields, under ultrahigh vacuum conditions, and with spatial resolution below one nanometer. [Preview Abstract] |
Thursday, March 24, 2005 4:18PM - 4:30PM |
W44.00010: Correction for thermal drift in scanning probe microscopy using polynomial mapping Daniel R. Katz, Matthew L. Trawick We present a method for correcting distortion due to thermal drift in scanning probe microscopy images. The strategy involves imaging an area once as one normally would, and then rescanning a narrow portion of the same area with the fast and slow scan axes reversed. The original image can then be corrected via polynomial mapping, where the coefficients of the polynomial mapping function are determinmed by a pointwise comparison of the full and partial images, with the partial image acting as a fiducial reference. [Preview Abstract] |
Thursday, March 24, 2005 4:30PM - 4:42PM |
W44.00011: Relative humidity control for atomic force microscopes Oleg Stukalov, Chris Murray, Amy Jacina, John Dutcher A cell for the control of relative humidity (RH) has been designed for use with atomic force microscopes (AFM) in which the tip is scanned across the stationary sample. The cell consists of a chamber with a small volume (4 cm$^{3})$ for accommodating the sample, the cantilever holder and a commercial humidity/temperature sensor. The RH is controlled by passing a controlled ratio of dry and humid nitrogen gas across the sample. This unique design prevents exposure of the AFM scanner assembly to humid air. Using this system, the RH at the sample position can be varied between 10{\%} and 90{\%} and controlled to within $\pm $0.2{\%} during the course of an AFM measurement. A study of the swelling of thin chitosan films as a function of RH is presented as a demonstration of the performance of the cell. [Preview Abstract] |
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W44.00012: High speed simultaneous optical and impedance measurements of single bio-particles Nicolas Green, Hywel Morgan, David Holmes We have developed a new method for the rapid detection of single bio-particles flowing in a micro-channel. Confocal optical detection has been combined with multi-frequency impedance based detection to allow measurements of single bio-particles. The optical detection setup is based around a high numerical aperture microscope objective with free space optical elements allowing dual wavelength excitation and three colour optical detection. The electrical impedance was measured using micro-electrodes integrated into the channel. Fluorescently labelled latex beads and human blood conjugated with CD+ antibodies have been measured with the device. The ability of the technique to correlate both optical and impedance data from individual particles passing through a detection region has applications in many fields, including micro and nanotechnology. [Preview Abstract] |
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