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Oct 2006

Volume 77, Issue 10, Articles (10xxxx)

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Superconducting quantum interference device instruments and applications

R. L. Fagaly

Rev. Sci. Instrum. 77, 101101 (2006); http://dx.doi.org/10.1063/1.2354545 (45 pages) | Cited 30 times

Online Publication Date: 11 October 2006

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Superconducting quantum interference devices (SQUIDs) have been a key factor in the development and commercialization of ultrasensitive electric and magnetic measurement systems. In many cases, SQUID instrumentation offers the ability to make measurements where no other methodology is possible. We review the main aspects of designing, fabricating, and operating a number of SQUID measurement systems. While this article is not intended to be an exhaustive review on the principles of SQUID sensors and the underlying concepts behind the Josephson effect, a qualitative description of the operating principles of SQUID sensors and the properties of materials used to fabricate SQUID sensors is presented. The difference between low and high temperature SQUIDs and their suitability for specific applications is discussed. Although SQUID electronics have the capability to operate well above 1 MHz, most applications tend to be at lower frequencies. Specific examples of input circuits and detection coil configuration for different applications and environments, along with expected performance, are described. In particular, anticipated signal strength, magnetic field environment (applied field and external noise), and cryogenic requirements are discussed. Finally, a variety of applications with specific examples in the areas of electromagnetic, material property, nondestructive test and evaluation, and geophysical and biomedical measurements are reviewed.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.50.+r Tunneling phenomena; Josephson effects
74.81.Fa Josephson junction arrays and wire networks
85.25.Cp Josephson devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
84.71.Ba Superconducting magnets; magnetic levitation devices
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Calibration of optical tweezers with positional detection in the back focal plane

Simon F. Tolić-Nørrelykke, Erik Schäffer, Jonathon Howard, Francesco S. Pavone, Frank Jülicher, and Henrik Flyvbjerg

Rev. Sci. Instrum. 77, 103101 (2006); http://dx.doi.org/10.1063/1.2356852 (11 pages) | Cited 45 times

Online Publication Date: 9 October 2006

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We explain and demonstrate a new method of force and position calibrations for optical tweezers with back-focal-plane photodetection. The method combines power spectral measurements of thermal motion and the response to a sinusoidal motion of a translation stage. It consequently does not use the drag coefficient of the trapped object as an input. Thus, neither the viscosity, nor the size of the trapped object, nor its distance to nearby surfaces needs to be known. The method requires only a low level of instrumentation and can be applied in situ in all spatial dimensions. It is both accurate and precise: true values are returned, with small error bars. We tested this experimentally, near and far from surfaces in the lateral directions. Both position and force calibrations were accurate to within 3%. To calibrate, we moved the sample with a piezoelectric translation stage, but the laser beam could be moved instead, e.g., by acousto-optic deflectors. Near surfaces, this precision requires an improved formula for the hydrodynamical interaction between an infinite plane and a microsphere in nonconstant motion parallel to it. We give such a formula.
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06.20.fb Standards and calibration
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.10.Pz Instruments for strain, force, and torque
42.79.Pw Imaging detectors and sensors
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
85.60.Gz Photodetectors (including infrared and CCD detectors)

Development of scanning x-ray fluorescence microscope with spatial resolution of 30 nm using Kirkpatrick-Baez mirror optics

S. Matsuyama, H. Mimura, H. Yumoto, Y. Sano, K. Yamamura, M. Yabashi, Y. Nishino, K. Tamasaku, T. Ishikawa, and K. Yamauchi

Rev. Sci. Instrum. 77, 103102 (2006); http://dx.doi.org/10.1063/1.2358699 (5 pages) | Cited 17 times

Online Publication Date: 11 October 2006

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We developed a high-spatial-resolution scanning x-ray fluorescence microscope (SXFM) using Kirkpatrick-Baez mirrors. As a result of two-dimensional focusing tests at BL29XUL of SPring-8, the full width at half maximum of the focused beam was achieved to be 50×30 nm2 (V×H) under the best focusing conditions. The measured beam profiles were in good agreement with simulated results. Moreover, beam size was controllable within the wide range of 30–1400 nm by changing the virtual source size, although photon flux and size were in a trade-off relationship. To demonstrate SXFM performance, a fine test chart fabricated using focused ion beam system was observed to determine the best spatial resolution. The element distribution inside a logo mark of SPring-8 in the test chart, which has a minimum linewidth of approximately 50–60 nm, was visualized with a spatial resolution better than 30 nm using the smallest focused x-ray beam.
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07.85.Tt X-ray microscopes
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
42.79.Bh Lenses, prisms and mirrors

Analysis of thermal aberrations in a high average power single-stage Ti:sapphire regenerative chirped pulse amplifier: Simulation and experiment

Vidya Ramanathan, Jinho Lee, Shengbo Xu, Xiaoming Wang, Luke Williams, William Malphurs, and D. H. Reitze

Rev. Sci. Instrum. 77, 103103 (2006); http://dx.doi.org/10.1063/1.2360989 (7 pages) | Cited 1 time

Online Publication Date: 24 October 2006

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We present a systematic investigation of thermal loading effects in single-stage high average power regenerative chirped pulse amplifiers based on Ti:sapphire. Using finite element analysis (FEA), we compute the temperature distributions, optical path deformations (OPDs), and corresponding thermal focal lengths for a variety of pumping conditions. We experimentally characterize thermal aberrations in a regenerative amplifier using a variety of techniques (interferometry, pump-probe thermal lens power, and M2 analysis). We find excellent agreement between the FEA modeling and experimental measurements of OPDs. Our methods allow us to predict the optimal pumping conditions for minimizing thermal aberrations for a variety of geometries and pumping conditions.
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42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
02.70.Dh Finite-element and Galerkin methods
42.60.By Design of specific laser systems
42.55.Rz Doped-insulator lasers and other solid state lasers

Three-channel x-ray crystal spectrometer for diagnosing high energy density plasmas

E. Baronova, B. Bucher, D. Haas, D. Fedin, A. Stepanenko, and F. N. Beg

Rev. Sci. Instrum. 77, 103104 (2006); http://dx.doi.org/10.1063/1.2360969 (5 pages) | Cited 1 time

Online Publication Date: 27 October 2006

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A novel spectrometer is designed, with three convex crystals. This spectrometer records simultaneous time integrated and time resolved spectra and can work as a polarimeter. The resolution, dispersion, and energy range of the spectrometer have been calculated using a ray tracing technique. The spectrometer has been used on an 80 kA current x-pinch pulser to record the L-shell spectra of various wire materials (Al, Ni, Cu, Mo, and W).
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52.70.La X-ray and γ-ray measurements
07.85.Nc X-ray and γ-ray spectrometers
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.58.Lq Z-pinches, plasma focus, and other pinch devices

Enhanced optical waveguide light mode spectroscopy via detection of fluorophore absorbance

Martin Halter, Michael Gabi, Marcus Textor, Janos Vörös, and H. Michelle Grandin

Rev. Sci. Instrum. 77, 103105 (2006); http://dx.doi.org/10.1063/1.2360886 (6 pages) | Cited 1 time

Online Publication Date: 27 October 2006

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A novel technique based on surface sensitive absorbance detection using an optical waveguide light mode spectroscopy (OWLS) instrument is presented. The proof of concept for this extension of a standard technique is demonstrated by painting an increasing number of ink lines on a waveguide, perpendicular to the light path, while monitoring the outcoupled light intensity. Furthermore, by the adsorption of poly(L-lysine)-graft-poly(ethylene glycol) as a model system with contents of 5%, 10%, 25%, and 50% labeled polymer, the in situ performance is demonstrated, and the absorbance signal is calibrated such that it can be converted into adsorbed mass. The simultaneous detection of labeled and label-free species allows for the study of complex experimental setups whereby monitoring of adsorption, desorption, and even exchange processes becomes possible. The sensitivity of the absorbance detection exceeds standard OWLS by one to two orders of magnitude.
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07.60.Rd Visible and ultraviolet spectrometers
42.79.Gn Optical waveguides and couplers
36.20.Kd Electronic structure and spectra

On-ground characterization of Rosetta/VIRTIS-M. II. Spatial and radiometric calibrations

G. Filacchione, E. Ammannito, A. Coradini, F. Capaccioni, G. Piccioni, M. C. De Sanctis, M. Dami, and A. Barbis

Rev. Sci. Instrum. 77, 103106 (2006); http://dx.doi.org/10.1063/1.2360786 (9 pages) | Cited 5 times

Online Publication Date: 27 October 2006

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After having considered the spectral and geometrical performances of the Rosetta/VIRTIS-M experiment, we complete here the analysis by evaluating quantitatively the flat-field and radiometric responses. The purpose of this work is to retrieve the flat-field matrix necessary to homogenize the focal plane response. Moreover, the most important result is the determination of the instrument transfer function that allows to convert digital numbers in physical units of spectral radiance (W m−2 μm−1 sterad−1). The strategy adopted to organize measurement sequence, a basic description of the on-ground experimental setups and the analysis of the collected data, is included in this article. An analysis of the instrumental stability has been performed as well by examining how the internal calibration data are affected by environmental conditions. These data allow to evaluate the cumulative effects of thermal and vibrational stresses on the instrumental performances: up to now we have verified that this effect is negligible. Finally the basic calibration pipeline used to calibrate in-flight data with on-ground parameters is fully described.
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95.75.Fg Spectroscopy and spectrophotometry
06.20.fb Standards and calibration
07.60.Rd Visible and ultraviolet spectrometers
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
95.55.Aq Charge-coupled devices, image detectors, and IR detector arrays
42.79.Pw Imaging detectors and sensors

Fast surface temperature measurement of Teflon propellant-in-pulsed ablative discharges using HgCdTe photovoltaic cells

Erik L. Antonsen, Rodney L. Burton, Garrett A. Reed, and Gregory G. Spanjers

Rev. Sci. Instrum. 77, 103107 (2006); http://dx.doi.org/10.1063/1.2360781 (9 pages) | Cited 2 times

Online Publication Date: 30 October 2006

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High-speed mercury cadmium telluride photovoltaic detectors, sensitive to infrared emission, are investigated as a means of measuring surface temperature on a microsecond time frame during pulsed ablative discharges with Teflon™ as the ablated material. Analysis is used to derive a governing equation for detector output voltage for materials with wavelength dependent emissivity. The detector output voltage is experimentally calibrated against thermocouples embedded in heated Teflon. Experimental calibration is performed with Teflon that has been exposed to ∼ 200 pulsed discharges and non-plasma-exposed Teflon and is compared to theoretical predictions to analyze emissivity differences. The diagnostic capability is evaluated with measurements of surface temperature from the Teflon propellant of electric micropulsed plasma thrusters. During the pulsed current discharge, there is insufficient information to claim that the surface temperature is accurately measured. However, immediately following the discharge, the postpulse cooling curve is measured. The statistical spread of postpulse surface temperature from shot to shot, most likely due to arc constriction and localization, is investigated to determine an operational envelope for postpulse temperature and mass ablation. This information is useful for determining postpulse ablation contributions to mass loss as well as evaluation of theoretical discharge models currently under development.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.75.Di Ion and plasma propulsion
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.50.Dg Plasma sources
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Absolute calibration for a broad range single shot electron spectrometer

Y. Glinec, J. Faure, A. Guemnie-Tafo, V. Malka, H. Monard, J. P. Larbre, V. De Waele, J. L. Marignier, and M. Mostafavi

Rev. Sci. Instrum. 77, 103301 (2006); http://dx.doi.org/10.1063/1.2360988 (6 pages) | Cited 42 times

Online Publication Date: 17 October 2006

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This article gives a detailed description of a single shot electron spectrometer which was used to characterize electron beams produced by laser-plasma interaction. Contrary to conventional electron sources, electron beams from laser-plasma accelerators can produce a broad range of energies. Therefore, diagnosing these electron spectra requires specific attention and experimental development. Here, we provide an absolute calibration of the Lanex Kodak Fine screen on a laser-triggered radio frequency picosecond electron accelerator. The efficiency of scintillating screens irradiated by electron beams has never been investigated so far. This absolute calibration is then compared to charge measurements from an integrating current transformer for quasimonoenergetic electron spectra from laser-plasma interaction.
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07.81.+a Electron and ion spectrometers
07.77.Ka Charged-particle beam sources and detectors
29.30.Aj Charged-particle spectrometers: electric and magnetic
29.30.Ep Charged-particle spectroscopy
29.20.-c Accelerators
52.38.Ph X-ray, γ-ray, and particle generation
52.38.Kd Laser-plasma acceleration of electrons and ions

Development of a low energy ion source for ROSINA ion mode calibration

Martin Rubin, Kathrin Altwegg, Annette Jäckel, and Hans Balsiger

Rev. Sci. Instrum. 77, 103302 (2006); http://dx.doi.org/10.1063/1.2358708 (8 pages)

Online Publication Date: 26 October 2006

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The European Rosetta mission on its way to comet 67P/Churyumov-Gerasimenko will remain for more than a year in the close vicinity (1 km) of the comet. The two ROSINA mass spectrometers on board Rosetta are designed to analyze the neutral and ionized volatile components of the cometary coma. However, the relative velocity between the comet and the spacecraft will be minimal and also the velocity of the outgassing particles is below 1 km/s. This combination leads to very low ion energies in the surrounding plasma of the comet, typically below 20 eV. Additionally, the spacecraft may charge up to a few volts in this environment. In order to simulate such plasma and to calibrate the mass spectrometers, a source for ions with very low energies had to be developed for the use in the laboratory together with the different gases expected at the comet. In this paper we present the design of this ion source and we discuss the physical parameters of the ion beam like sensitivity, energy distribution, and beam shape. Finally, we show the first ion measurements that have been performed together with one of the two mass spectrometers.
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29.25.Ni Ion sources: positive and negative
95.55.Ym Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques
06.20.fb Standards and calibration
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Derivation of time-dependent two-dimensional velocity field maps for plasma turbulence studies

T. Munsat and S. J. Zweben

Rev. Sci. Instrum. 77, 103501 (2006); http://dx.doi.org/10.1063/1.2356851 (13 pages) | Cited 10 times

Online Publication Date: 2 October 2006

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Time-resolved two-dimensional (2D) velocity maps have been derived for fluctuation measurements in the edge plasma of the National Spherical Torus Experiment (NSTX). The maps have been derived from time sequences of 2D images recorded with the gas puff imaging diagnostic. A hybrid technique combining optical flow and local pattern matching has been implemented to overcome the individual limitations of each when used with data of limited temporal and/or spatial resolution. Local flow velocities of up to ∼ 8 km/s and average poloidal flow velocities of up to ∼ 5 km/s are found. Results are compared to previous velocity extraction techniques and NSTX results.
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52.35.Ra Plasma turbulence
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Fi Transport properties
52.25.Gj Fluctuation and chaos phenomena
52.40.Hf Plasma-material interactions; boundary layer effects
52.55.Fa Tokamaks, spherical tokamaks

Multichord optical interferometry of FRX-L’s field reversed configuration

E. L. Ruden, Shouyin Zhang, G. A. Wurden, T. P. Intrator, R. Renneke, W. J. Waganaar, F. T. Analla, and T. C. Grabowski

Rev. Sci. Instrum. 77, 103502 (2006); http://dx.doi.org/10.1063/1.2354568 (5 pages) | Cited 3 times

Online Publication Date: 4 October 2006

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A 0.633 μm laser interferometer provides detailed time resolved information about the spatial distribution of the plasma density of field reversed configurations (FRC’s) produced by the FRX-L experiment at Los Alamos National Laboratory. This experiment is an effort to produce a magnetized plasma with closed field lines suitable for compression by a solid metal liner imploded by the Shiva Star capacitor bank at the Air Force Research Laboratory. The interferometer probes a fanned array of eight chords through the FRC midplane, measuring the line integrated free electron density via its effect on optical phase shift relative to eight reference beams as a function of time. The reference beams are given nominally identical optical paths, except that they are folded for compactness and given an 80 MHz higher optical frequency by use of a Bragg cell beam splitter. After the beams are recombined, interference results in 80 MHz electromagnetic beat waves with dynamic phase shifts equal to those of the corresponding optical probes. Quadrature mixing of the electronically monitored light is then performed with rf components. Noteworthy features of the interferometer’s design are the unique compact folding scheme of the reference paths, inclusion of a fused quartz tube in the reference path similar to that of the FRC’s vacuum vessel to compensate for cylindrical lensing, and transmission of the interfering light via optical fibers to a rf shielded room for processing. Extraneous contributions to the phase shift due to vibration resulting from the system’s pulsed magnetic field, and dynamic refractive changes in or near the fused quartz tube wall (possibly due to radiation heating) are corrected for.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.60.Ly Interferometers
52.55.Ez Theta pinch
52.25.Xz Magnetized plasmas
52.50.Lp Plasma production and heating by shock waves and compression
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Virtual instrument for the diagnosis of surface wave discharges

O. Carabaño, J. Ballesteros, A. Gamero, and A. Sola

Rev. Sci. Instrum. 77, 103503 (2006); http://dx.doi.org/10.1063/1.2362720 (4 pages) | Cited 3 times

Online Publication Date: 24 October 2006

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This article presents an experimental system that controls the automatic measuring procedure for the electromagnetic and optical diagnosis of a surface wave discharge by using a LABVIEW virtual instrument. The system also processes the measured data to determine some parameters that characterize the plasma, based on previously developed techniques. The structure of the system is implemented in such a way that permits the diagnosis of the surface wave discharges in both continuous and pulsed modes. The system has been tested and validated in a cylindrical discharge but it can be used to carry out measurement in a coaxial configuration too.
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52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Pi High-frequency and RF discharges
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma

Hard x-ray diagnostic for lower hybrid experiments on Alcator C-Mod

J. Liptac, R. Parker, V. Tang, Y. Peysson, and J. Decker

Rev. Sci. Instrum. 77, 103504 (2006); http://dx.doi.org/10.1063/1.2214695 (7 pages) | Cited 8 times

Online Publication Date: 30 October 2006

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Alcator C-Mod’s lower hybrid current drive (LHCD) system allows the exploration of advanced tokamak (AT) regimes at densities relevant to ITER and fusion reactors. The location of the LHCD is critical to AT performance and may be inferred by measuring the nonthermal bremsstrahlung emission in the hard x-ray (HXR) region. A pinhole camera using an array of 32 CdZnTe detectors is used to image energies in the 20–200 keV range. Detectors and pulse processing electronics are integrated into a compact and modular package making extensive use of printed circuit board and surface mount technology. The system also makes use of fast digitization and software signal processing techniques. An ambient environment of neutrons, gammas, and high rf power requires careful shielding. Shielding is studied using the neutron and photon transport code MCNP. The design of the diagnostic is presented along with background measurements in lieu of LHCD fast electrons. Background measurements are then compared to advanced modeling results to predict the power threshold for meaningful HXR data for a H-mode target plasma.
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52.70.La X-ray and γ-ray measurements
52.59.Px Hard X-ray sources
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.55.Fa Tokamaks, spherical tokamaks
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Fi Transport properties
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Wideband and hysteresis-free regulation of piezoelectric actuator based on induced current for high-speed scanning probe microscopy

Masami Kageshima, Shinsuke Togo, Yan Jun Li, Yoshitaka Naitoh, and Yasuhiro Sugawara

Rev. Sci. Instrum. 77, 103701 (2006); http://dx.doi.org/10.1063/1.2356850 (6 pages) | Cited 2 times

Online Publication Date: 2 October 2006

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A novel closed-loop regulation of a piezoelectric actuator is presented to implement wideband and hysteresis-free motion required for high-speed operation of scanning probe microscopy. Velocity of the actuator’s displacement detected via the induced current and its integration giving the displacement were used to actively compensate the resonances and hysteresis. The validity of the idea was demonstrated using a prototype circuit composed of operational amplifiers and multilayered piezoelectric actuators. The fundamental resonance of the actuator at 260 kHz was completely eliminated from the actuator’s displacement with an appropriate velocity feedback. With an additional displacement feedback the gain error was suppressed within ±5 dB over a frequency range from dc to 1 MHz, while a −45° bandwidth was also maintained as wide as 250 kHz. In addition, intrinsic hysteresis of the actuator measured with an 8 kHz sinusoidal signal was suppressed to below 1%. Responses in displacement of the actuator to burst oscillation and square wave inputs exhibited clear improvement from the uncompensated responses.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
07.79.-v Scanning probe microscopes and components
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Nanoprobes for near-field optical microscopy manufactured by substitute-sheath etching and hollow cathode sputtering

M. Chaigneau, G. Ollivier, T. Minea, and G. Louarn

Rev. Sci. Instrum. 77, 103702 (2006); http://dx.doi.org/10.1063/1.2354569 (5 pages) | Cited 6 times

Online Publication Date: 2 October 2006

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This article reports a new approach for probe manufacturing, which is the key component in scanning near-field optical microscope (SNOM). The wet-etching process, to create the tip at the apex of a tapered fiber, has been optimized. Typical tip features are short tapers, large cone angles (30°), and very small diameters (<50 nm). Next process steps are performed in an original arrangement of plasma device, based on a modified hollow cathode discharge. It is used for both, to remove the dust particles or the etching residues from the tip surface and to coat the tapered region with a metallic ultrathin and compact film. To complete the probe’s fabrication, the tips are opened by dry electrolytic erosion. These probes have been successfully tested for SNOM applications.
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07.79.Fc Near-field scanning optical microscopes

Analysis of the through-focus images with boundary-element method in high resolution optical metrology

Deh-Ming Shyu and Mao-Hong Lu

Rev. Sci. Instrum. 77, 103703 (2006); http://dx.doi.org/10.1063/1.2354570 (7 pages)

Online Publication Date: 5 October 2006

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For through-focus focus metric we build a measurement system, in which a single diffraction-limited micro lens is used for imaging and a grating with a few pitches is used as a target. In this system, the optical field is calculated by the boundary-element method, in which a new algorithm is developed to reduce the dimension of a matrix. As a result, the memory capacity required in this calculation is much reduced up to 83% in our simulation case. An optimization of the grating structure is made to obtain the highest sensitivity for the critical dimension metrology. With the optimized grating structure the simulation shows a sensitivity of less than 1 nm in the through-focus focus metric.
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07.60.Pb Conventional optical microscopes
42.79.Bh Lenses, prisms and mirrors
42.79.Dj Gratings

Tip characterizer for atomic force microscopy

Hiroshi Itoh, Toshiyuki Fujimoto, and Shingo Ichimura

Rev. Sci. Instrum. 77, 103704 (2006); http://dx.doi.org/10.1063/1.2356855 (4 pages) | Cited 15 times

Online Publication Date: 9 October 2006

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A tip characterizer for atomic force microscopy (AFM) was developed based on the fabrication of multilayer thin films. Comb-shaped line and space (LS) and wedge-shaped knife-edge structures were fabricated on a GaAs substrate. GaAs/InGaP superlattices were used to control the width of the structures precisely, and selective chemical etching was used to form sharp edges on the nanostructures. The minimum size of the LS structure was designed to be 10 nm, and the radius of the knife edge was less than 5 nm. These nanostructures were used as a well-defined tip characterizer to measure the shape of a tip on a cantilever from line profiles of AFM images.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
68.65.Cd Superlattices
81.65.Cf Surface cleaning, etching, patterning
61.46.-w Structure of nanoscale materials

New technique for studying nanoscale friction at sliding velocities up to 200 mm/s using atomic force microscope

Zhenhua Tao and Bharat Bhushan

Rev. Sci. Instrum. 77, 103705 (2006); http://dx.doi.org/10.1063/1.2358690 (9 pages) | Cited 11 times

Online Publication Date: 11 October 2006

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Micro-/nanoelectromechanical devices and components operate at high sliding velocities. Studies of tribological properties of materials by atomic force microscope (AFM) are limited to low velocity regime (<100–250 μm/s) due to inherent instrument limitation of AFM. To overcome the limitation of AFM working velocity, a custom-calibrated ultrahigh velocity stage has been incorporated for tribological investigation up to 200 mm/s. The stage is driven by a piezoactuator which is controlled using proportional-integral-derivative algorithm. Friction data are obtained by processing the AFM laser photodiode signals using a high sampling rate data acquisition system. The friction data obtained from the modified setup at high sliding velocities are compared with the results from conventional AFM friction measurement. The effects of scan size, rest time, and velocity on the friction force and adhesive force for single crystal silicon (100) with native oxide have been studied.
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81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness

Efficient electrochemical etching method to fabricate sharp metallic tips for scanning probe microscopes

Pilkyu Kim, Jun Ho Kim, Mun Seok Jeong, Do-Kyeong Ko, Jongmin Lee, and Sungho Jeong

Rev. Sci. Instrum. 77, 103706 (2006); http://dx.doi.org/10.1063/1.2358703 (5 pages) | Cited 7 times

Online Publication Date: 11 October 2006

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A new technique based on electrochemical etching for the fabrication of sharp metallic tips for scanning probe microscopes is introduced. In the proposed method, a small Teflon mass is attached to the end of an immersed tungsten wire using an aluminum tape, which leads to a significant enhancement of yield rate of sharp tungsten tips with an apex size below 100 nm to over 60%. The functionality of the tungsten tips fabricated by the proposed method is verified by measuring the topography of a standard sample using a shear-force scanning probe microscope.
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81.65.Cf Surface cleaning, etching, patterning
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Quantitative measurements of indentation moduli by atomic force acoustic microscopy using a dual reference method

Gheorghe Stan and William Price

Rev. Sci. Instrum. 77, 103707 (2006); http://dx.doi.org/10.1063/1.2360971 (6 pages) | Cited 15 times

Online Publication Date: 17 October 2006

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Atomic force acoustic microscopy (AFAM) was used to quantitatively determine material indentation moduli by measuring local mechanical responses. A dual reference method has been shown to be capable of extracting the modulus of a material within 3% of the calculated expected value without any assumptions of the probe’s mechanical properties. The use of this developed method also allows for the calculation of the maximum precision in the quantitative determination of the indentation modulus of materials using AFAM. A parallel analysis of the single and dual reference AFAM techniques isolates the inaccuracy induced by the assumption that the indentation modulus of the atomic force microscopy probe used is the same as bulk silicon.
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07.79.Lh Atomic force microscopes
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness

Using an electroconductive carbon nanotube probe tip in scanning nonlinear dielectric microscopy

K. Ishikawa and Y. Cho

Rev. Sci. Instrum. 77, 103708 (2006); http://dx.doi.org/10.1063/1.2360985 (4 pages) | Cited 1 time

Online Publication Date: 18 October 2006

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A scanning nonlinear dielectric microscope (SNDM), which can be used for detecting the surface and subsurface of ferroelectric polarization with high resolution, has been developed. Contact-mode atomic force microscopy typically uses a metal-coated conductive cantilever tip; however, SNDM imaging resolution declines upon repeated scanning because of the abrasion of the tip in the contact mode. To improve the lateral resolution of the tip, we used an electroconductive carbon nanotube (CNT) probe tip. Using the SNDM with the CNT probe, the ferroelectric domain boundary of stoichiometric lithium tantalate (LiTaO3) is observed in air at room temperature and the results compared with those obtained using a platinum-coated tip.
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07.79.-v Scanning probe microscopes and components
68.37.-d Microscopy of surfaces, interfaces, and thin films
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis

Methods of determining the contact between a probe and a surface under scanning electron microscopy

C.-H. Nien, C. H. Tsai, K. Y. Shin, and W. B. Jian

Rev. Sci. Instrum. 77, 103709 (2006); http://dx.doi.org/10.1063/1.2360883 (7 pages)

Online Publication Date: 24 October 2006

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Based on the charging effect common to various kinds of electron microscopy, we have developed novel methods of determining “when” and “where” a probe starts to contact an electrically isolated surface. The touchdown of an electrically grounded probe leads to an acute change in the imaging contrast of the contacted surface, which also causes a rapid jump (ranging from a few to tens of picoamperes) of the grounding current. Thus, the detection of contact can be carried out in both qualitative and quantitative manners, providing a basis for establishing relevant standard procedures. In addition, we have achieved the spatial mapping of the contact point(s) using a specially designed lithographical pattern with two mutually vertical sets of parallel conductive lines. The precision of this mapping technique is simply determined by the pitch of parallel lines, which can be as small as the capability achievable in e-beam lithography. A possible “one-probe” version of the electrical characterization is also discussed with the same underlying principle, which may turn out to be indispensable for various studies and applications of nanostructures. Further development along this track is promising to realize an instrumentally simple version of “scanning electron spectroscopy” with various modes.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
61.46.-w Structure of nanoscale materials
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Versatile magneto-optic Kerr effect polarimeter for studies of domain-wall dynamics in magnetic nanostructures

Corneliu Nistor, Geoffrey S. D. Beach, and James L. Erskine

Rev. Sci. Instrum. 77, 103901 (2006); http://dx.doi.org/10.1063/1.2356856 (11 pages) | Cited 11 times

Online Publication Date: 2 October 2006

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This article describes a versatile instrument capable of probing magnetic domain-wall dynamics in microstructured thin films. The instrument combines a state-of-the-art scanning magneto-optic Kerr effect polarimeter that incorporates high-bandwidth signal detection, an integrated broadband magnet system, and a microwave probe station. Together, these subsystems enable a broad range of studies of field and current-driven domain-wall dynamics in submicrometer magnetic structures and devices. Domain-wall motion can be probed with ≈ 2 μm spatial resolution and less than 2 ns temporal resolution. That motion can be driven by magnetic fields of up to ≈ 100 Oe amplitude with sinusoidal (>20 MHz) or user-defined wave forms (20 ns rise time) or by electric currents from dc to ≈ 10 GHz. A detailed description of the instrument is provided as well as several experiments highlighting its capabilities, including hysteresis loop shape and magnetic energy loss measurements spanning ten decades of drive frequency; spatially and temporally resolved measurements of domain-wall propagation in submicrometer magnetic wires; and mobility measurements of field- and current-driven domain-wall motion.
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07.60.Fs Polarimeters and ellipsometers
78.20.Ls Magneto-optical effects
75.60.Ch Domain walls and domain structure
75.50.Tt Fine-particle systems; nanocrystalline materials
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Development and validation of an experimental setup for the biaxial fatigue testing of metal thin films

S. Eve, N. Huber, O. Kraft, A. Last, D. Rabus, and M. Schlagenhof

Rev. Sci. Instrum. 77, 103902 (2006); http://dx.doi.org/10.1063/1.2357313 (8 pages) | Cited 3 times

Online Publication Date: 2 October 2006

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In this article, we describe a new experimental setup which has been developed to investigate the fatigue behavior of thin metal films on polymer substrates as used in micro-optical components. The setup is based on the ring-on-ring test and includes an optical in situ failure detection system. The method is validated for thin Au films by comparing the in situ results with microscopical analyses using scanning electron and atomic force microscopies.
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81.70.Bt Mechanical testing, impact tests, static and dynamic loads
42.82.Bq Design and performance testing of integrated-optical systems
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Ps Atomic force microscopy (AFM)
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