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Mar 2012

Volume 83, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 83, 031301 (2012); http://dx.doi.org/10.1063/1.3688856 (11 pages)

Ronald P. Manginell, Matthew W. Moorman, Jerome A. Rejent, Paul T. Vianco, Mark J. Grazier, Brian D. Wroblewski, Curtis D. Mowry, and Komandoor E. Achyuthan

Microsamplers with low-power, low-outgassing, hermetic microvalves are poised for field sampling of light gases in applications including altitude-resolved collection of gases relevant to climate and weather.   The microsamplers are shown on a mirror, reflecting the weather on a spring day in Albuquerque, New Mexico. (Photo: Randy Montoya, Sandia Laboratories.)

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back to top Microscopy and Imaging

Miniature active damping stage for scanning probe applications in ultra high vacuum

Maximilian Assig, Andreas Koch, Wolfgang Stiepany, Carola Straßer, Alexandra Ast, Klaus Kern, and Christian R. Ast

Rev. Sci. Instrum. 83, 033701 (2012); http://dx.doi.org/10.1063/1.3689769 (6 pages)

Online Publication Date: 2 March 2012

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Scanning probe microscope (SPM) experiments demand a low vibration level to minimize the external influence on the measured signal. We present a miniature six-degree of freedom active damping stage based on a Gough-Stewart platform (hexapod) which is positioned in ultra high vacuum as close to the SPM as possible. In this way, vibrations originating from the experimental setup can be effectively reduced providing a quiet environment for the SPM. In addition, the hexapod provides a rigid reference point, which facilitates wiring as well as sample transfer. We outline the main working principle and show that for scanning tunneling microscopy (STM) measurements of a Si(111) 7 × 7 surface, the hexapod significantly improves the stability and quality of the topographic images.
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07.79.Cz Scanning tunneling microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Determining the equation of state of amorphous solids at high pressure using optical microscopy

Samrat A. Amin, Erin N. Rissi, Keri McKiernan, and Jeffery L. Yarger

Rev. Sci. Instrum. 83, 033702 (2012); http://dx.doi.org/10.1063/1.3688656 (5 pages)

Online Publication Date: 6 March 2012

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A method to determine the volumetric equation of state of amorphous solids using optical microscopy in a diamond anvil cell is described. The method relies on two- dimensional image acquisition and analysis to quantify changes in the projected image area with compression. The area analysis methods prove to be robust against improper focusing and lighting conditions while providing the accuracy necessary to deduce small area changes, which correspond to small volume changes in an isotropic material. The image capture, area analysis method is used to determine the compression of cubic crystals, yielding results in good agreement with diffraction and volumetric measurements. As a proof of concept, the equation of state of amorphous red phosphorus is measured up to 12 GPa under hydrostatic conditions where the quantified volume change between the red and black phases is approximately ΔV/V0 ≈ 0.05 after a reduction of volume nearing 35% at 8 GPa. A large hysteresis is present during decompression and eventually results in a 15% permanent densification relative to the starting volume, which is attributed to a pressure induced crystallization from red to black phosphorus. The robustness of the technique is also demonstrated by measuring the equation of state of GeSe2 glasses for semi transparent samples and As2O3 in which gold coating is used as a contrasting aid.
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42.30.Va Image forming and processing
42.30.Wb Image reconstruction; tomography

An in-vacuum x-ray diffraction microscope for use in the 0.7–2.9 keV range

D. J. Vine, G. J. Williams, J. N. Clark, C. T. Putkunz, M. A. Pfeifer, D. Legnini, C. Roehrig, E. Wrobel, E. Huwald, G. van Riessen, B. Abbey, T. Beetz, J. Irwin, M. Feser, B. Hornberger, et al.

Rev. Sci. Instrum. 83, 033703 (2012); http://dx.doi.org/10.1063/1.3688655 (5 pages) | Cited 5 times

Online Publication Date: 14 March 2012

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A dedicated in-vacuum coherent x-ray diffraction microscope was installed at the 2-ID-B beamline of the Advanced Photon Source for use with 0.7–2.9 keV x-rays. The instrument can accommodate three common implementations of diffractive imaging; plane wave illumination; defocused-probe (Fresnel diffractive imaging) and scanning (ptychography) using either a pinhole, focused or defocused probe. The microscope design includes active feedback to limit motion of the optics with respect to the sample. Upper bounds on the relative optics-to-sample displacement have been measured to be 5.8 nm(v) and 4.4 nm(h) rms/h using capacitance micrometry and 27 nm/h using x-ray point projection imaging. The stability of the measurement platform and in-vacuum operation allows for long exposure times, high signal-to-noise and large dynamic range two-dimensional intensity measurements to be acquired. Finally, we illustrate the microscope's stability with a recent experimental result.
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07.85.Tt X-ray microscopes
42.25.Fx Diffraction and scattering
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.68.+m Photography, photographic instruments; xerography
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Background-free imaging of plasmonic structures with cross-polarized apertureless scanning near-field optical microscopy

M. Esslinger, J. Dorfmüller, W. Khunsin, R. Vogelgesang, and K. Kern

Rev. Sci. Instrum. 83, 033704 (2012); http://dx.doi.org/10.1063/1.3693346 (6 pages) | Cited 4 times

Online Publication Date: 15 March 2012

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We present advances in experimental techniques of apertureless scanning near-field optical microscopy (aSNOM). The rational alignment procedure we outline is based upon a phase singularity that occurs while scanning polarizers around the nominal cross-polarized configuration of s-polarized excitation and p-polarized detection. We discuss the theoretical origin of this topological feature of the setup, which is robust against small deviations, such as minor tip misalignment or shape variations. Setting the polarizers to this singular configuration point eliminates all background signal, allowing for reproducible plasmonic eigenmode mapping with optimal signal-to-noise ratio.
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07.79.Fc Near-field scanning optical microscopes
42.79.Ci Filters, zone plates, and polarizers

Superficial magnetic imaging by an xy-scanner of three magnetoresistive channels

M. E. Cano, A. H. Pacheco, T. Cordova, E. E. Mazon, and A. Barrera

Rev. Sci. Instrum. 83, 033705 (2012); http://dx.doi.org/10.1063/1.3694002 (6 pages)

Online Publication Date: 15 March 2012

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A scanning system developed for planar magnetic surfaces composed of a moving line of three magnetoresistive ultrasensitive transducers, complemented by a signal conditioning circuit is presented. After the calibration of the sensors, it was used to determine magnetized surface images with different shapes to evaluate the sensitivity of the device, and the images are represented in gray levels on a scale from 0 to 255 intensities, to get a visual representation of the magnetic field strength. The device is shown to be sensitive enough to detect gradients homogeneities and discontinuities in the magnetic field maps and images of magnetic susceptibility.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
42.30.Wb Image reconstruction; tomography
06.20.fb Standards and calibration

Methods and instrumentation for piezoelectric motors

B. Drevniok, W. M. P. Paul, K. R. Hairsine, and A. B. McLean

Rev. Sci. Instrum. 83, 033706 (2012); http://dx.doi.org/10.1063/1.3694972 (6 pages)

Online Publication Date: 19 March 2012

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Because of their compact form factor and rigidity, piezoelectric motors are used in scanning probe microscopes that operate at low temperature and high magnetic field. Here we present detailed information to facilitate the assembly, operation, and characterization of inertial motors. Specifically, a model of the motor is developed and used to identify different regions of operation. Drive electronics with high slew rate and large output current are described and a step-by-step procedure for assembling piezoelectric shear stacks is detailed. Additionally, a novel reflective object sensor is described and used to characterize a Pan-style inertial motor that was designed and assembled using the concepts presented in this paper.
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07.79.-v Scanning probe microscopes and components
84.50.+d Electric motors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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Ultra compact multitip scanning tunneling microscope with a diameter of 50 mm

Vasily Cherepanov, Evgeny Zubkov, Hubertus Junker, Stefan Korte, Marcus Blab, Peter Coenen, and Bert Voigtländer

Rev. Sci. Instrum. 83, 033707 (2012); http://dx.doi.org/10.1063/1.3694990 (5 pages) | Cited 2 times

Online Publication Date: 19 March 2012

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We present a multitip scanning tunneling microscope (STM) where four independent STM units are integrated on a diameter of 50 mm. The coarse positioning of the tips is done under the control of an optical microscope or scanning electron microscopy in vacuum. The heart of this STM is a new type of piezoelectric coarse approach called KoalaDrive. The compactness of the KoalaDrive allows building a four-tip STM as small as a single-tip STM with a drift of less than 0.2  nm/min at room temperature and lowest resonance frequencies of 2.5  kHz (xy) and 5.5  kHz (z). We present as examples of the performance of the multitip STM four point measurements of silicide nanowires and graphene.
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07.79.Cz Scanning tunneling microscopes
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
61.48.Gh Structure of graphene

An x-space magnetic particle imaging scanner

Patrick W. Goodwill, Kuan Lu, Bo Zheng, and Steven M. Conolly

Rev. Sci. Instrum. 83, 033708 (2012); http://dx.doi.org/10.1063/1.3694534 (9 pages) | Cited 4 times

Online Publication Date: 22 March 2012

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Magnetic particle imaging (MPI) is an imaging modality with great promise for high-contrast, high-sensitivity imaging of iron oxide tracers in animals and humans. In this paper, we present the first x-space MPI hardware and reconstruction software; show experimentally measured signals; detail our reconstruction technique; and present images of resolution and “angiography” phantoms.
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87.59.Dj Angiography
87.59.bd Computed radiography
87.61.-c Magnetic resonance imaging
87.57.nf Reconstruction
87.57.cf Spatial resolution

Dual frequency open-loop electric potential microscopy for local potential measurements in electrolyte solution with high ionic strength

Naritaka Kobayashi, Hitoshi Asakawa, and Takeshi Fukuma

Rev. Sci. Instrum. 83, 033709 (2012); http://dx.doi.org/10.1063/1.3698207 (6 pages)

Online Publication Date: 30 March 2012

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Recent development of open-loop electric potential microscopy (OL-EPM) has enabled to measure local potential distribution at a solid/liquid interface. However, the operating environment of OL-EPM has been limited to a weak electrolyte solution (<1 mM). This has significantly limited its application range in biology and chemistry. To overcome this limitation, we have developed dual frequency (DF) mode OL-EPM. In the method, an ac bias voltage consisting of two frequency components at f1 and f2 is applied between a tip and sample. The local potential is calculated from the amplitudes of the f1 and |f1 − f2| components of the electrostatic force. In contrast to the conventional single frequency (SF) mode OL-EPM, the detection of the 2f1 component is not required in DF mode. Thus, the maximum bias modulation frequency in DF mode is twice as high as that in SF mode. The high bias modulation frequency used in DF mode prevents the generation of electrochemical reactions and redistribution of ions and water, which enables to operate OL-EPM even in a strong electrolyte solution. In this study, we have performed potential measurements of nanoparticles on a graphite surface in 1 and 10 mM NaCl solution. The results demonstrate that DF mode OL-EPM allows measurements of local potential distribution in 10 mM electrolyte solution.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.79.Lh Atomic force microscopes
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