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Mar 2005

Volume 76, Issue 3, Articles (03xxxx)

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In situ and real-time characterization of metal-organic chemical vapor deposition growth by high resolution x-ray diffraction

A. Kharchenko, K. Lischka, K. Schmidegg, H. Sitter, J. Bethke, and J. Woitok

Rev. Sci. Instrum. 76, 033101 (2005); http://dx.doi.org/10.1063/1.1857277 (4 pages) | Cited 3 times

Online Publication Date: 2 February 2005

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We present an x-ray diffractometer for the analysis of epitaxial layers during (in situ) metal-organic chemical vapor deposition (MOCVD). Our diffractometer has a conventional x-ray source, does not need a goniometer stage, and is not sensitive to precise adjustment of the samples before measurement. It allows us to perform measurements within a few seconds even from rotating and wobbling samples. The first results of laboratory tests performed with our x-ray diffraction system show that it is well suited for in situ and real-time monitoring of the MOCVD growth process. We were able to measure the growth rate of a cubic GaN layer and the intensity and peak position of Bragg reflections of the growing layer in less than 20 s only.
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07.85.Jy Diffractometers
61.05.cp X-ray diffraction
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology

Using fluorescence lifetime for discriminating detector afterpulsing in fluorescence-correlation spectroscopy

Jörg Enderlein and Ingo Gregor

Rev. Sci. Instrum. 76, 033102 (2005); http://dx.doi.org/10.1063/1.1863399 (5 pages) | Cited 20 times

Online Publication Date: 15 February 2005

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Fluorescence correlation spectroscopy (FCS) has become an important and widely used technique for many applications in physics, chemistry, and biology. Usually, FCS is measured with sensitive light detectors working in the photon-counting Geiger mode. A common property of such detectors is afterpulsing: the generation of spurious photon detection events after a genuine photon detection. Such afterpulsing causes a significant deviation of the measured autocorrelation function from its true value on a short time scale and can seriously influence derived parameters for fast processes such as triplet-state photophysics. Here, we discuss the impact of afterpulsing on FCS in detail. A new method is developed to eliminate afterpulsing effects by using time-correlated single-photon counting for separating the true fluorescence signal from afterpulsing events.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.Dq Photometers, radiometers, and colorimeters

Two-prism setup for surface plasmon resonance studies

Bhaskar Chandra Mohanty and S. Kasiviswanathan

Rev. Sci. Instrum. 76, 033103 (2005); http://dx.doi.org/10.1063/1.1865853 (4 pages) | Cited 2 times

Online Publication Date: 15 February 2005

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A two-prism experimental arrangement having wide angular scan ranges for the study of surface plasmon resonance is presented. The setup has a single rotating element instead of a high cost goniometer and a stationary photodetector which is positioned such that it always receives the reflected beam normally. The usefulness of the setup has been verified by experimental and theoretical studies of plasmon resonance at an Au–air interface.
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42.79.Bh Lenses, prisms and mirrors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

High-power frequency-stabilized laser for laser cooling of metastable helium at 389 nm

J. C. J. Koelemeij, W. Hogervorst, and W. Vassen

Rev. Sci. Instrum. 76, 033104 (2005); http://dx.doi.org/10.1063/1.1865752 (4 pages) | Cited 2 times

Online Publication Date: 22 February 2005

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A high-power, frequency-stabilized laser for cooling of metastable helium atoms using the 2 math→3 math transition at 389 nm has been developed. The 389 nm light is generated by frequency doubling of a titanium:sapphire laser in an external enhancement cavity containing a lithium–triborate nonlinear crystal. With a maximum conversion efficiency of 75%, 1 W of useful 389 nm power is produced out of 2 W at 778 nm. While being stabilized to the 2 math→3 math transition, the 389 nm frequency is tunable over ±150 MHz with respect to the field-free atomic resonance frequency. This is accomplished by Zeeman tuning of the absorption lines used in the frequency-stabilization scheme. The setup for saturated absorption spectroscopy in an rf discharge cell, used to stabilize the 389 nm laser to the atomic transition, is described in detail.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Fc Modulation, tuning, and mode locking
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
37.10.De Atom cooling methods
37.10.Gh Atom traps and guides
37.10.Vz Mechanical effects of light on atoms, molecules, and ions

Simple pressure-tuned Fabry–Pérot interferometer

E. Hansis, T. Cubel, J.-H. Choi, J. R. Guest, and G. Raithel

Rev. Sci. Instrum. 76, 033105 (2005); http://dx.doi.org/10.1063/1.1866237 (3 pages) | Cited 4 times

Online Publication Date: 1 March 2005

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A simple, compact and inexpensive pressure-tuned Fabry–Pérot interferometer is presented. It is used as a laser locking reference for optical frequencies where the use of an atomic reference is impractical. The scanning range is several GHz. Absolute positioning of the interferometer with an accuracy of 7 MHz rms over a range of 2 GHz is possible. The instrument is temperature stabilized and shows long-term drift of 16 MHz rms over 48 h.
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07.60.Ly Interferometers

TCSPC upgrade of a confocal FCS microscope

Aleš Benda, Martin Hof, Michael Wahl, Matthias Patting, Rainer Erdmann, and Peter Kapusta

Rev. Sci. Instrum. 76, 033106 (2005); http://dx.doi.org/10.1063/1.1866814 (4 pages) | Cited 15 times

Online Publication Date: 1 March 2005

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We extended the measurement capabilities of the Carl Zeiss ConfoCor 1 FCS microscope by (a) using pulsed picosecond diode lasers instead of a continuous wave (CW) laser excitation, (b) introducing a fast single photon avalanche diode detector, and (c) exploiting the capabilities of the PicoQuant TimeHarp 200 board. When the time-tagged time-resolved (TTTR) mode of the TimeHarp is utilized, the complete fluorescence dynamics are recorded. That is, the time-evolution of the fluctuations and the fluorescence decay kinetics are captured simultaneously. Recording individual photon events (without on-the-fly data reduction like in hardware correlators) preserves the full information content of the measurement for virtually unlimited data analysis tasks and provides a much more detailed view of processes happening in the detection volume. For example, autocorrelation functions of dyes in a mixture can be separated and/or their cross-correlation can be investigated. These virtual two-channel measurements are performed utilizing a single detection channel setup. The time-resolved FCS is a powerful tool in biological studies and is demonstrated here on unilamellar vesicles giving clear evidence for Bodipy dye exchange between them. The described upgrade scenario is applicable to other confocal microscopes as well. In principle, any FCS system so far utilizing conventional CW lasers can benefit from pulsed excitation and the original functionality of the setup is fully preserved.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers
87.64.mk Confocal
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
06.60.Jn High-speed techniques (microsecond to femtosecond)
07.60.Dq Photometers, radiometers, and colorimeters

Programmable spectral interferometric microscopy

Nabeel A. Riza, Maarten Bakker, and Amana Bokhari

Rev. Sci. Instrum. 76, 033107 (2005); http://dx.doi.org/10.1063/1.1866832 (10 pages)

Online Publication Date: 1 March 2005

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A programmable optical sensor is proposed based on spectrally programmable heterodyne optical interferometric confocal microscopy implemented via an ultrastable in-line acousto-optic tunable filter (AOTF) based interferometer using double anisotropic acousto-optic Bragg diffraction. The design uses a tunable laser as the light source and anisotropic diffractions in an AOTF to generate two near-collinear orthogonal linear polarization and slightly displaced beams that both pass via the test sample to deliver highly sensitive sample birefringence or material optical retardation measurements. A spherical lens is used to form focused spots for high resolution confocal spatial sampling of the test object. Thus the instrument also forms a classic interferometric confocal microscope via the use of single mode fiber optics for the receive light. The laser and AOTF tuning allows birefringence measurements taken at different wavelengths, one at a time with minimal interwavelength crosstalk. Experimental demonstration of the instrument is achieved using a 1550 nm center 100 nm band tunable laser and variable birefringence liquid crystal and fixed retardance birefringent materials, all showing accurate retardation measurements to within a 0.5° rf phase accuracy. The instrument shows a fiber-in to fiber-out loss of 8.5 dB. An alternate design via a transmissive beam generation design provides collinear co-located beams on the sample plane for superaccurate measurements.
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07.60.Ly Interferometers
07.60.Vg Fiber-optic instruments
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.81.Gs Birefringence, polarization
07.60.Pb Conventional optical microscopes
42.81.Pa Sensors, gyros
42.81.Dp Propagation, scattering, and losses; solitons
42.60.Fc Modulation, tuning, and mode locking
42.79.Jq Acousto-optical devices
42.79.Ci Filters, zone plates, and polarizers

External Raman standard for absolute intensity and concentration measurements

Ryan N. Favors, Yanan Jiang, Yvette L. Loethen, and Dor Ben-Amotz

Rev. Sci. Instrum. 76, 033108 (2005); http://dx.doi.org/10.1063/1.1866952 (5 pages) | Cited 7 times

Online Publication Date: 1 March 2005

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A new method of calibrating Raman intensities is described, which uses a sapphire window as an external intensity standard. This method overcomes problems often encountered using conventional internal standards techniques, resulting either from refractive index differences or chemical interactions of the standard with the sample. The new method is demonstrated by measuring solution concentrations and Raman cross sections in various liquids. Concentration measurements are performed using the second derivative variance minimization (SDVM) algorithm to simultaneously subtract the sapphire window spectrum, normalize the solution spectral intensity and quantify solute concentration. The absolute Raman cross sections of several pure liquids were determined by comparing intensities of the sapphire-normalized Raman bands to that of benzene and other liquids whose Raman cross sections are known.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
06.20.F- Units and standards
42.79.Ci Filters, zone plates, and polarizers
82.80.Gk Analytical methods involving vibrational spectroscopy
78.30.C- Liquids
78.30.Jw Organic compounds, polymers

Frequency reference for laser spectroscopy with the stabilized 4-m-long Fabry–Perot cavity

Paweł Kruk, Andrzej Noga, Teresa Trepka, Jerzy Zachorowski, and Wojciech Gawlik

Rev. Sci. Instrum. 76, 033109 (2005); http://dx.doi.org/10.1063/1.1866992 (4 pages)

Online Publication Date: 1 March 2005

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A 4-m-long, stabilized Fabry–Perot interferometer for frequency reference in high-resolution laser spectroscopy is described. The interferometer works as a transfer cavity locked to one laser whose frequency is Doppler-free stabilized to an atomic transition. Another laser beam whose frequency is scanned across the investigated spectral range is transmitted across the cavity to yield the frequency markers with FSR intervals below 40 MHz. The two laser beams of very close frequencies are separated at the cavity exit by a polarization method. The described methodology is simple yet versatile and provides dense and stable frequency markers for high-resolution laser spectroscopy.
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07.60.Ly Interferometers
42.62.Fi Laser spectroscopy
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Characterization of GaAsP trap detector for radiometric measurements in ultraviolet wavelength region

M. Noorma, P. Kärhä, A. Lamminpää, S. Nevas, and E. Ikonen

Rev. Sci. Instrum. 76, 033110 (2005); http://dx.doi.org/10.1063/1.1866972 (5 pages) | Cited 2 times

Online Publication Date: 2 March 2005

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A trap detector was constructed of three Schottky-type 10×10 mm2 GaAsP photodiodes. The spectral reflectance of the trap detector was calculated from the measured spectral reflectances of a single GaAsP photodiode in the wavelength range between 240 and 600 nm, and compared to the measured spectral reflectance of the trap detector at three laser wavelengths. The absolute spectral responsivity of the trap detector was measured. The internal quantum efficiencies (IQE) of the trap detector and a single photodiode were calculated in the wavelength region between 250 and 400 nm from the spectral reflectances and responsivities. The comparison revealed reduction of the apparent IQE of the trap detector as compared to the single photodiode at the level of 10%. The spatial uniformity of the responsivity of the trap detector was measured, and the corresponding uncertainty component at 325 nm was calculated to be 4×10−4. The effect of moderate ultraviolet exposure at the level of 50 mJ/cm2 on the stability of the responsivity of GaAsP photodiode was studied and found to be below 2×10−3 at all used wavelengths.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.60.Dq Photometers, radiometers, and colorimeters
85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Hi Surface barrier, boundary, and point contact devices

200 kHz electro-optic switch for ultrafast laser systems

Detlef Nickel, Christian Stolzenburg, Angelika Beyertt, Adolf Giesen, Jürgen Häußermann, Frank Butze, and Martin Leitner

Rev. Sci. Instrum. 76, 033111 (2005); http://dx.doi.org/10.1063/1.1867052 (7 pages) | Cited 5 times

Online Publication Date: 2 March 2005

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A method for obtaining very high electro-optic switching rates is demonstrated and employed for regenerative amplification of ultrashort pulses at high repetition rates. The intracavity polarization switch consists of a transverse-field BBO Pockels cell and a dielectric thin film polarizer. By multiple-shift usage of a single BBO crystal as Pockels cell, it is possible to keep thermal dissipation losses in the Pockels cell driver below 200 W. Using this intracavity polarization switch in an ultrafast thin-disk Yb:KYW regenerative amplifier, pulse energies of about 9 μJ with pulse durations of 280 fs at repetition rates of 200 kHz were generated.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.79.Ci Filters, zone plates, and polarizers
06.60.Jn High-speed techniques (microsecond to femtosecond)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
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Magnetic field stabilization by temperature control of an azimuthally varying field cyclotron magnet

S. Okumura, K. Arakawa, M. Fukuda, Y. Nakamura, W. Yokota, T. Ishimoto, S. Kurashima, I. Ishibori, T. Nara, T. Agematsu, M. Sano, and T. Tachikawa

Rev. Sci. Instrum. 76, 033301 (2005); http://dx.doi.org/10.1063/1.1858578 (6 pages) | Cited 3 times

Online Publication Date: 2 February 2005

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A magnetic field drift, gradual decrease of the order of 10−4 in several tens of hours, was observed with the beam intensity decrease in an operation of an azimuthally varying field (AVF) cyclotron. From our experimental results, we show that the temperature increase of the magnet iron by the heat transfer from the excitation coils can induce such change of the magnetic field as to deteriorate the beam quality. The temperature control of the magnet iron was realized by thermal isolation between the main coil and the yoke and by precise control of the cooling water temperature of the trim coils attached to the pole surfaces in order to prevent temperature change of the magnet iron. The magnetic field stability of ±5×10−6 and the beam intensity stability of ±2% have been achieved by this temperature control.
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07.55.Db Generation of magnetic fields; magnets
07.07.Tw Servo and control equipment; robots
29.20.dg Cyclotrons

A secondary electron emission detector for measuring the intensity of synchrotron radiation

Nobuteru Nariyama and Shingo Taniguchi

Rev. Sci. Instrum. 76, 033302 (2005); http://dx.doi.org/10.1063/1.1866648 (3 pages) | Cited 1 time

Online Publication Date: 22 February 2005

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A secondary electron emission detector can be used as a high-intensity radiation beam monitor because the absence of ion recombination extends the upper dose range of the monitor. The characteristics of saturation, linearity, sensitivity, reproducibility, and current stability of the monitor were measured with respect to synchrotron radiation from undulators at SPring-8. Thin aluminum-evaporated electrodes were used in a vacuum chamber. Linearity was observed at 1011–1013 photons/s between 10 and 30 keV. Even at the highest intensity of 1015 photons/s, current linearity was achieved to some extent. Sensitivity ranged from 27 to 55 pC/Gy/cm2, and increased with decreasing energy. During long irradiation, the current decreased gradually with time; the degree became larger with the dose. When irradiation was interrupted, however, the current recovered to its initial value at the next irradiation.
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07.77.Ka Charged-particle beam sources and detectors
07.85.Qe Synchrotron radiation instrumentation
79.20.Hx Electron impact: secondary emission

Production of photoemission-modulated beams in a thermionic electron gun

J. G. Neumann, J. R. Harris, B. Quinn, and P. G. O’Shea

Rev. Sci. Instrum. 76, 033303 (2005); http://dx.doi.org/10.1063/1.1866652 (8 pages) | Cited 8 times

Online Publication Date: 2 March 2005

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The generation and evolution of perturbations and modulations in intense charged particle beams are of key importance for many accelerator applications. Prior work focused on perturbations and modulations produced in gridded electron guns with thermionic cathodes. By using a drive laser, photoemission can produce perturbations within a longer beam generated by thermionic emission. These perturbations affect beam density only, while previous experiments with gridded guns produced perturbations in both beam density and velocity. We have extended these capabilities by developing a flexible system to produce multiple perturbations whose timing and amplitude can be easily adjusted for beam research applications. In this article we describe this apparatus and give preliminary results.
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84.47.+w Vacuum tubes
79.40.+z Thermionic emission
41.75.Jv Laser-driven acceleration
79.60.-i Photoemission and photoelectron spectra
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A Penning-assisted subkilovolt coaxial plasma source

Zhehui Wang, Paul D. Beinke, Cris W. Barnes, Michael W. Martin, Edward Mignardot, Glen A. Wurden, Scott C. Hsu, Thomas P. Intrator, and Carter P. Munson

Rev. Sci. Instrum. 76, 033501 (2005); http://dx.doi.org/10.1063/1.1855071 (7 pages) | Cited 9 times

Online Publication Date: 2 February 2005

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A Penning-assisted 20 MW coaxial plasma source (plasma gun), which can achieve breakdown at sub-kV voltages, is described. The minimum breakdown voltage is about 400 V, significantly lower than previously reported values of 1–5 kV. The Penning region for electrons is created using a permanent magnet assembly, which is mounted to the inside of the cathode of the coaxial plasma source. A theoretical model for the breakdown is given. A 900 V 0.5 F capacitor bank supplies energy for gas breakdown and plasma sustainment from 4 to 6 ms duration. Typical peak gun current is about 100 kA and gun voltage between anode and cathode after breakdown is about 200 V. A circuit model is used to understand the current-voltage characteristics of the coaxial gun plasma. Energy deposited into the plasma accounts for about 60% of the total capacitor bank energy. This plasma source is uniquely suitable for studying multi-MW multi-ms plasmas with sub-MJ capacitor bank energy.
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52.50.Dg Plasma sources
52.80.Sm Magnetoactive discharges (e.g., Penning discharges)
52.75.-d Plasma devices
07.55.-w Magnetic instruments and components
52.65.-y Plasma simulation
52.25.Fi Transport properties

Enhanced magnetic ionization in hydrogen reflex discharge plasma source

E. I. Toader and V. N. Covlea

Rev. Sci. Instrum. 76, 033502 (2005); http://dx.doi.org/10.1063/1.1866236 (4 pages) | Cited 1 time

Online Publication Date: 15 February 2005

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The effect of enhanced magnetic ionization on the external and internal parameters of a high-density, low pressure reflex plasma source operating in hydrogen is studied. The Langmuir probe method and Druyvesteyn procedure coupled with suitable software are used to measure the internal parameters. The bulk plasma region is free of an electric field and presents a high degree of uniformity. The electron energy distribution function is bi-Maxwellian with a dip∕shoulder structure around 5.5 eV, independent of external parameters and radial position. Due to the enhanced hollow cathode effect by the magnetic trapping of electrons, the electron density ne is as high as 1018 m−3, and the electron temperature Te is as low as a few tens of an electron volt, for dissipated energy of tens of Watts. The bulk plasma density scales with the dissipated power.
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51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
52.50.Dg Plasma sources
52.50.Nr Plasma heating by DC fields; ohmic heating, arcs

Spin-exchange optically pumped polarized math target for low-energy charged particle scattering experiments

T. Katabuchi, S. Buscemi, J. M. Cesaratto, T. B. Clegg, T. V. Daniels, M. Fassler, R. B. Neufeld, and S. Kadlecek

Rev. Sci. Instrum. 76, 033503 (2005); http://dx.doi.org/10.1063/1.1866235 (7 pages) | Cited 3 times

Online Publication Date: 1 March 2005

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We have constructed, tested, and calibrated a polarized math target system which facilitates p-math elastic scattering at proton energies as low as 2 MeV. This system consists of a target cell placed in a uniform B field inside a scattering chamber and an external optical pumping station utilizing Rb spin exchange. Computer-controlled valves allow polarized math gas to be transferred quickly between the optical pumping station and the spherical Pyrex target cell, which has Kapton film covering apertures for the passing beam and the scattering particles. The magnetic field required to maintain math polarization in the target cell is created with a compact, shielded sine-theta coil. Target gas polarimetry is accomplished using nuclear magnetic resonance and calibrated using the known analyzing power of α-math scattering.
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29.25.Pj Polarized and other targets
25.10.+s Nuclear reactions involving few-nucleon systems
25.40.Cm Elastic proton scattering
27.10.+h A ≤ 5

Active radiometric calorimeter for absolute calibration of radioactive sources

K. E. Stump, L. A. DeWerd, D. A. Rudman, and S. A. Schima

Rev. Sci. Instrum. 76, 033504 (2005); http://dx.doi.org/10.1063/1.1867032 (9 pages) | Cited 4 times

Online Publication Date: 1 March 2005

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This report describes the design and initial noise floor measurements of a radiometric calorimeter designed to measure therapeutic medical radioactive sources. The instrument demonstrates a noise floor of approximately 2 nW. This low noise floor is achieved by using high temperature superconducting (HTS) transition edge sensor (TES) thermometers in a temperature-control feedback loop. This feedback loop will be used to provide absolute source calibrations based upon the electrical substitution method. Other unique features of the calorimeter are (a) its ability to change sources for calibration without disrupting the vacuum of the instrument, and (b) the ability to measure the emitted power of a source in addition to the total contained source power.
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87.80.-y Biophysical techniques (research methods)
87.57.un Radiopharmaceuticals
07.20.Fw Calorimeters
07.60.Dq Photometers, radiometers, and colorimeters
87.53.Jw Therapeutic applications, including brachytherapy
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.20.Dt Thermometers
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3ω-scanning thermal microscope

Stéphane Lefèvre and Sebastian Volz

Rev. Sci. Instrum. 76, 033701 (2005); http://dx.doi.org/10.1063/1.1857151 (6 pages) | Cited 19 times

Online Publication Date: 2 February 2005

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We present the theoretical and experimental calibrations of a scanning thermal microscope (SThM) based on a hot anemometer wire probe. Under ac heating and due to the linear dependence of the probe electrical resistance to temperature, the third harmonic of the tip voltage is also linear to the temperature. This method called “3-ω” is currently used to estimate the thermal properties with a hot strip deposited on the sample surface. However, in this last technique, the sensor size allows one to reach the sample transient thermal behavior whereas the SThM tip does not. We propose a thermal model showing what information can in fact be obtained by using the microscope under the 3ω mode. We finally report an experimental calibration providing the tip/sample contact thermal parameters.
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07.20.Dt Thermometers
07.79.-v Scanning probe microscopes and components

Millimeter-wave scanning near-field anisotropy microscopy

Tatsuo Nozokido, Ryohei Iibuchi, Jongsuck Bae, Koji Mizuno, and Hiroyuki Kudo

Rev. Sci. Instrum. 76, 033702 (2005); http://dx.doi.org/10.1063/1.1866255 (6 pages) | Cited 2 times

Online Publication Date: 22 February 2005

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A millimeter-wave scanning near-field microscopy using a slit-type probe, which permits the observation of electrical anisotropy in the viewed object, is proposed. The slit probe is sensitive to any electrical anisotropy along the object surface direction that is inherent in the object to be imaged, because the electric field at its aperture is linearly polarized. An electrical anisotropy model is incorporated into the image reconstruction process that enables two-dimensional image reconstruction. The details of the model and the reconstruction method adopted in this work are described and experimental results to demonstrate the feasibility of this microscopy format are presented.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.79.Fc Near-field scanning optical microscopes
07.05.Pj Image processing
42.30.Wb Image reconstruction; tomography
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Electron precession: A guide for implementation

C. S. Own, L. D. Marks, and Wharton Sinkler

Rev. Sci. Instrum. 76, 033703 (2005); http://dx.doi.org/10.1063/1.1866612 (13 pages) | Cited 6 times

Online Publication Date: 1 March 2005

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The design approach for electron precession systems designed at Northwestern University is described, and examples of systems retrofitted onto two different transmission electron microscopes using this method are demonstrated. The precession diffraction patterns from these instruments are of good quality while simultaneously being very easy to acquire. A 15-minute procedure for aligning these instruments is described in the appendix. Partnering this user-friendly and inexpensive hardware implementation with fast and user-friendly crystallography software offers potentially speedy and routine solution of crystal structures.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
61.05.J- Electron diffraction and scattering

Stand-alone device for the electrolytic fabrication of scanning near-field optical microscopy aperture probes

C. Haumann, Ch. Pelargus, H. G. Frey, R. Ros, D. Anselmetti, J. Toquant, and D. W. Pohl

Rev. Sci. Instrum. 76, 033704 (2005); http://dx.doi.org/10.1063/1.1866253 (4 pages) | Cited 6 times

Online Publication Date: 1 March 2005

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Near-field optical applications require the fast, stable, and reproducible fabrication of scanning near-field optical microscopy (SNOM) aperture probes in the submicrometer range. We have developed a stand-alone device for the electrolytic etching of nanoapertures with an integrated current and optical transmission monitoring and control. Probes with an aperture ranging from 50 to 100 nm were reproducibly fabricated with great reliability. With these probes, high resolution SNOM images of 100 nm test patterns and single dye molecules (Rhodamine 6G in poly(vinyl alcohol)) are measured and presented. Not requiring a SNOM setup, the stand-alone device is not only inexpensive and compact, but also insensitive to external disturbances.
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07.79.Fc Near-field scanning optical microscopes
82.47.Wx Electrochemical engineering
82.45.Gj Electrolytes
81.65.Cf Surface cleaning, etching, patterning
42.81.Bm Fabrication, cladding, and splicing

Development of a metal–tip cantilever for noncontact atomic force microscopy

Kotone Akiyama, T. Eguchi, T. An, Y. Fujikawa, Y. Yamada-Takamura, T. Sakurai, and Y. Hasegawa

Rev. Sci. Instrum. 76, 033705 (2005); http://dx.doi.org/10.1063/1.1865812 (3 pages) | Cited 18 times

Online Publication Date: 2 March 2005

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We report on a focused-ion-beam fabrication of a metal–tip cantilever for noncontact atomic force microscopy (AFM) and demonstrate its superior performance by observing atomically resolved AFM images of the Si(111)7×7 surface. Characterization of the tip apex by transmission electron microscope revealed that the tip radius is less than 5 nm. Detrimental changes in the resonance frequency and the Q factor of the cantilever due to the attachment of the metal tip are small and do not affect the performance of the AFM imaging. Since the fabrication technique is applicable to any materials, various functional probes can be developed with this method.
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07.10.Cm Micromechanical devices and systems
07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
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Spin-echo small angle neutron scattering in Delft

M. Theo Rekveldt, Jeroen Plomp, Wim G. Bouwman, Wicher H. Kraan, Serguei Grigoriev, and Menno Blaauw

Rev. Sci. Instrum. 76, 033901 (2005); http://dx.doi.org/10.1063/1.1858579 (9 pages) | Cited 18 times

Online Publication Date: 2 February 2005

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We describe two spin-echo instruments for neutron small angle scattering, which have been installed at the reactor institute in Delft. The first setup is using a monochromatic beam and magnetized foils as spin flippers, while the second uses resonant spin flippers in a pulsed neutron beam. The components that play an essential role for operation are described in some detail. Each setup has specific advantages in its range of spin-echo lengths that covers the range of correlation lengths that could be measured. This is demonstrated in a comparative measurement, the setup with magnetized foils measuring at spin-echo-lengths up to 20 μm and the setup with resonant flippers measuring in the range up to 0.5 μm.
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61.05.fg Neutron scattering (including small-angle scattering)
07.77.-n Atomic, molecular, and charged-particle sources and detectors
29.30.Hs Neutron spectroscopy
61.05.fd Theories of neutron diffraction and scattering

Volume-variable sample holder for small-angle x-ray scattering measurements of supercritical solutions and its application to the CHF3–CO2 mixture

Takeshi Morita, Tomoko Masakawa, Asako Ayusawa Arai, Masato Nakagawa, and Keiko Nishikawa

Rev. Sci. Instrum. 76, 033902 (2005); http://dx.doi.org/10.1063/1.1858580 (4 pages) | Cited 1 time

Online Publication Date: 2 February 2005

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A sample holder for small-angle x-ray scattering (SAXS) experiments was designed for a volume-variable operation by using a metal bellows. The key point of our design is such that no backup pressure is required. This made the sample cell and peripherals compact so that it can be placed in a limited space typical of synchrotron radiation facilities. Furthermore, the pressure/volume of the sample can be set at any desired value easily. This holder enabled us to carry out precise measurements of SAXS intensities of supercritical solutions with simple operations at many different densities. For performance test, correlation lengths, which provide information on spatial fluctuation of fluid, were evaluated for a supercritical CHF3–CO2 mixture at the 0.005 mole fraction of CHF3 over a wide-density region.
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06.60.Ei Sample preparation (including design of sample holders)
61.05.cf X-ray scattering (including small-angle scattering)
07.85.Qe Synchrotron radiation instrumentation
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