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Apr 2012

Volume 83, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 83, 041101 (2012); http://dx.doi.org/10.1063/1.3697599 (19 pages)

Michael A. Duncan

The laser vaporization cluster source in the "cutaway" configuration. The sample rod is mounted from above with a flexible nylon screw in a holding block. The pulsed gas valve is mounted in the stainless steel can (left) and the skimmer is mounted on the opposite wall.

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back to top Condensed Matter; Materials

A new pulsed laser deposition technique: Scanning multi-component pulsed laser deposition method

D. Fischer, G. F. de la Fuente, and M. Jansen

Rev. Sci. Instrum. 83, 043901 (2012); http://dx.doi.org/10.1063/1.3697861 (8 pages)

Online Publication Date: 3 April 2012

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The scanning multi-component pulsed laser deposition (PLD) method realizes uniform depositions of desired coatings by a modified pulsed laser deposition process, preferably with a femto-second laser-system. Multi-component coatings (single or multilayered) are thus deposited onto substrates via laser induced ablation of segmented targets. This is achieved via horizontal line-scanning of a focused laser beam over a uniformly moving target's surface. This process allows to deposit the desired composition of the coating simultaneously, starting from the different segments of the target and adjusting the scan line as a function of target geometry. The sequence and thickness of multilayers can easily be adjusted by target architecture and motion, enabling inter/intra layer concentration gradients and thus functional gradient coatings. This new, simple PLD method enables the achievement of uniform, large-area coatings. Case studies were performed with segmented targets containing aluminum, titanium, and niobium. Under the laser irradiation conditions applied, all three metals were uniformly ablated. The elemental composition within the rough coatings obtained was fixed by the scanned area to Ti-Al-Nb = 1:1:1. Crystalline aluminum, titanium, and niobium were found to coexist side by side at room temperature within the substrate, without alloy formation up to 600 °C.
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81.05.Bx Metals, semimetals, and alloys
81.15.Fg Pulsed laser ablation deposition

Thermal lens spectroscopy for the differentiation of biodiesel-diesel blends

M. Ventura, E. Simionatto, L. H. C. Andrade, and S. M. Lima

Rev. Sci. Instrum. 83, 043902 (2012); http://dx.doi.org/10.1063/1.3698002 (5 pages) | Cited 1 time

Online Publication Date: 3 April 2012

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Thermal lens (TL) spectroscopy was applied to biofuels to test its potential to distinguish diesel from biodiesel in blended fuels. Both the heat and mass diffusion effects observed using a TL procedure provide significant information about biodiesel concentrations in blended fuels. The results indicate that the mass diffusivity decreases 32% between diesel and the blend with 10% biodiesel added to the diesel. This simple TL procedure has the potential to be used for in loco analyses to certify the mixture and quality of biodiesel-diesel blends.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

A simple device for dielectric spectroscopy of polymers with temperature regulation close to 300 K based on a Peltier junction

A. Raihane, R. Tourbot, F. Ladieu, and D. L’Hôte

Rev. Sci. Instrum. 83, 043903 (2012); http://dx.doi.org/10.1063/1.3700217 (5 pages)

Online Publication Date: 9 April 2012

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We present a simple thermostat device for performing dielectric spectroscopy measurements on polymers close to their glass transition temperature. By using a vacuum chamber containing a Peltier junction with its regulator, we show that a very simple setup yields a temperature accuracy which is good enough for accurate studies of polymer dielectric properties. This technique is also more cost effective than standard setups using cryogenic fluids.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

A 30 T pulsed magnet with conical bore for synchrotron powder diffraction

J. Billette, F. Duc, P. Frings, M. Nardone, A. Zitouni, C. Detlefs, T. Roth, W. Crichton, J. E. Lorenzo, and G. L. J. A. Rikken

Rev. Sci. Instrum. 83, 043904 (2012); http://dx.doi.org/10.1063/1.3701830 (7 pages) | Cited 1 time

Online Publication Date: 9 April 2012

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We report on the design, construction, and operation of a horizontal field, 30 T magnet system with a conical bore optimized for synchrotron x-ray powder diffraction. The magnet offers ±31° optical access downstream of the sample, which allows to measure a sufficiently large number of Debye rings for an accurate crystal structure analysis. Combined with a 290 kJ generator, magnetic field pulses of 60 ms length were generated in the magnet, with a rise time of 4.1 ms and a repetition rate of 6 pulses/h at 30 T. The coil is mounted inside a liquid nitrogen bath. A liquid helium flow cryostat reaches into the coil and allows sample temperature between 5 and 250 K. The setup was used on the European Synchrotron Radiation Facility beamlines ID20 and ID06.
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85.70.Ay Magnetic device characterization, design, and modeling

Femtosecond-laser-driven photoelectron-gun for time-resolved cathodoluminescence measurement of GaN

T. Onuma, Y. Kagamitani, K. Hazu, T. Ishiguro, T. Fukuda, and S. F. Chichibu

Rev. Sci. Instrum. 83, 043905 (2012); http://dx.doi.org/10.1063/1.3701368 (7 pages) | Cited 2 times

Online Publication Date: 11 April 2012

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A rear-excitation femtosecond-laser-driven photoelectron gun (PE-gun) is developed for measuring time-resolved cathodoluminescence (TRCL) spectrum of wide bandgap materials and structures such as semiconductors and phosphors. The maximum quantum efficiency of a 20-nm-thick Au photocathode excited using a frequency-tripled Al2O3:Ti laser under a rear-excitation configuration is 3.6×10−6, which is a reasonable value for a PE-gun. When the distance between the front edge of the PE-gun and the observation point is 10 mm, the narrowest electron-beam (e-beam) diameter is 19 μm, which corresponds to one tenth of the laser-beam diameter and is comparable to the initial e-beam diameter of a typical W hair-pin filament of thermionic electron-gun. From the results of TRCL measurements on the freestanding GaN grown by the ammonothermal method and a GaN homoepitaxial film grown by metalorganic vapor phase epitaxy, overall response time for the present TRCL system is estimated to be 8 ps. The value is the same as that of time-resolved photoluminescence measurement using the same excitation laser pulses, meaning that the time-resolution is simply limited by the streak-camera, not by the PE-gun performance. The result of numerical simulation on the temporal e-beam broadening caused by the space-charge-effect suggests that the present PE-gun can be used as a pulsed e-beam source for spatio-time-resolved cathodoluminescence, when equipped in a scanning electron microscope.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors
84.47.+w Vacuum tubes
78.47.D- Time resolved spectroscopy (>1 psec)

Application of ring method to measure surface tensions of liquids in high magnetic field

Chuanjun Li, Long Chen, and Zhongming Ren

Rev. Sci. Instrum. 83, 043906 (2012); http://dx.doi.org/10.1063/1.4704081 (5 pages) | Cited 1 time

Online Publication Date: 13 April 2012

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The high-magnetic-field tensiometer (HMFT) has been developed to measure surface tensions of liquids in high magnetic field based on the ring method. The HMFT was composed of three parts: weighing system, liquid circulatory system, and supporting system. Some improvements for the conventional tensiometer were made in order to overcome the magnetic effects. The surface tension of acetone was measured using the HMFT. The results showed that the surface tension of acetone linearly varied with the magnetic field intensity and increased by 0.69 mN m−1 or 2.9% in the magnetic field of 10 T. The HMFT could better determine the surface tension of liquids with and without the magnetic field and it provided a simple and practical way to measure the surface tension of liquids at room temperature in a high magnetic field.
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68.03.Cd Surface tension and related phenomena
06.30.Dr Mass and density

Lock-in detection for pulsed electrically detected magnetic resonance

Felix Hoehne, Lukas Dreher, Jan Behrends, Matthias Fehr, Hans Huebl, Klaus Lips, Alexander Schnegg, Max Suckert, Martin Stutzmann, and Martin S. Brandt

Rev. Sci. Instrum. 83, 043907 (2012); http://dx.doi.org/10.1063/1.4704837 (4 pages) | Cited 1 time

Online Publication Date: 20 April 2012

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We show that in pulsed electrically detected magnetic resonance (pEDMR) signal modulation in combination with a lock-in detection scheme can reduce the low-frequency noise level by one order of magnitude and in addition removes the microwave-induced non-resonant background. This is exemplarily demonstrated for spin-echo measurements in phosphorus-doped silicon. The modulation of the signal is achieved by cycling the phase of the projection pulse used in pEDMR for the readout of the spin state.
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76.30.-v Electron paramagnetic resonance and relaxation

Rheology of fluids measured by correlation force spectroscopy

Milad Radiom, Brian Robbins, Christopher D. F. Honig, John Y. Walz, Mark R. Paul, and William A. Ducker

Rev. Sci. Instrum. 83, 043908 (2012); http://dx.doi.org/10.1063/1.4704085 (14 pages) | Cited 1 time

Online Publication Date: 23 April 2012

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We describe a method, correlation force spectrometry (CFS), which characterizes fluids through measurement of the correlations between the thermally stimulated vibrations of two closely spaced micrometer-scale cantilevers in fluid. We discuss a major application: measurement of the rheological properties of fluids at high frequency and high spatial resolution. Use of CFS as a rheometer is validated by comparison between experimental data and finite element modeling of the deterministic ring-down of cantilevers using the known viscosity of fluids. The data can also be accurately fitted using a harmonic oscillator model, which can be used for rapid rheometric measurements after calibration. The method is non-invasive, uses a very small amount of fluid, and has no actively moving parts. It can also be used to analyze the rheology of complex fluids. We use CFS to show that (non-Newtonian) aqueous polyethylene oxide solution can be modeled approximately by incorporating an elastic spring between the cantilevers.
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47.57.Qk Rheological aspects
47.11.Fg Finite element methods
02.70.Dh Finite-element and Galerkin methods
06.20.fb Standards and calibration
47.57.Ng Polymers and polymer solutions
47.50.Ef Measurements
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