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Top 20 Most Read Articles
September 2009
The 20 articles with the most full-text downloads during the month, in descending order.
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Rev. Sci. Instrum. 80, 081101 (2009); http://dx.doi.org/10.1063/1.3184828 (23 pages) Online Publication Date: 5 August 2009
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We review the current state of multiphoton microscopy. In particular, the requirements and limitations associated with high-speed multiphoton imaging are considered. A description of the different scanning technologies such as line scan, multifoci approaches, multidepth microscopy, and novel detection techniques is given. The main nonlinear optical contrast mechanisms employed in microscopy are reviewed, namely, multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation. Techniques for optimizing these nonlinear mechanisms through a careful measurement of the spatial and temporal characteristics of the focal volume are discussed, and a brief summary of photobleaching effects is provided. Finally, we consider three new applications of multiphoton microscopy: nonlinear imaging in microfluidics as applied to chemical analysis and the use of two-photon absorption and self-phase modulation as contrast mechanisms applied to imaging problems in the medical sciences.
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WSXM: A software for scanning probe microscopy and a tool for nanotechnology Rev. Sci. Instrum. 78, 013705 (2007); http://dx.doi.org/10.1063/1.2432410 (8 pages) Online Publication Date: 31 January 2007
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In this work we briefly describe the most relevant features of WSXM, a freeware scanning probe microscopy software based on MS-Windows. The article is structured in three different sections: The introduction is a perspective on the importance of software on scanning probe microscopy. The second section is devoted to describe the general structure of the application; in this section the capabilities of WSXM to read third party files are stressed. Finally, a detailed discussion of some relevant procedures of the software is carried out.
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A compact apparatus for studies of element and phase-resolved ferromagnetic resonance Rev. Sci. Instrum. 80, 083903 (2009); http://dx.doi.org/10.1063/1.3190402 (7 pages) Online Publication Date: 11 August 2009
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We present a compact sample holder equipped with electromagnets and high frequency transmission lines; the sample holder is intended for combined x-ray magnetic circular dichroism (XMCD) and ferromagnetic resonance measurements (FMR). Time-resolved measurements of resonant x-ray detected FMR during forced precession are enabled by use of a rf excitation that is phase-locked to the storage ring bunch clock. Several applications of the combined XMCD+FMR technique are presented, demonstrating the flexibility of the experimental design.
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A compact molecular beam machine Rev. Sci. Instrum. 80, 083105 (2009); http://dx.doi.org/10.1063/1.3206367 (5 pages) Online Publication Date: 31 August 2009
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We have developed a compact, low cost, modular, crossed molecular beam machine. The new apparatus utilizes several technological advancements in molecular beams valves, ion detection, and vacuum pumping to reduce the size, cost, and complexity of a molecular beam apparatus. We apply these simplifications to construct a linear molecular beam machine as well as a crossed-atomic and molecular beam machine. The new apparatus measures almost 50 cm in length, with a total laboratory footprint less than 0.25 m2 for the crossed-atomic and molecular beam machine. We demonstrate the performance of the apparatus by measuring the rotational temperature of nitric oxide from three common molecular beam valves and by observing collisional energy transfer in nitric oxide from a collision with argon.
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Design of a variable temperature scanning force microscope Rev. Sci. Instrum. 80, 083704 (2009); http://dx.doi.org/10.1063/1.3212561 (6 pages) Online Publication Date: 31 August 2009
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We have developed the variable temperature scanning force microscope capable of performing both magnetic resonance force microscopy (MRFM) and magnetic force microscopy (MFM) measurements in the temperature range between 5 and 300 K. Modular design, large scanning area, and interferometric detection of the cantilever deflection make it a sensitive, easy to operate, and reliable instrument suitable for studies of the dynamic and static magnetization in various systems. We have verified the performance of the microscope by imaging vortices in a Nb thin film in the MFM mode of operation. MRFM spectra in a diphenyl-picryl-hydrazyl film were recorded to evaluate the MRFM mode of operation.
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Rev. Sci. Instrum. 80, 093101 (2009); http://dx.doi.org/10.1063/1.3212667 (8 pages) Online Publication Date: 2 September 2009
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A complete system for the simultaneous monitoring of multiple cantilever sensors from different sensor arrays has been developed and tested for gas- and liquid-phase applications. The cantilever sensors are operated in static-deflection mode and the readout is achieved with phase-shifting interferometric microscopy (PSIM). In contrast to existing cantilever-sensor readout methods, PSIM is not dependent on alignment and allows the monitoring of the entire displacement profiles of all cantilevers within the field of view, using just one light source. To complement the PSIM readout, we have developed a sample cell, which can hold multiple cantilever-array chips, allows for very fast and reproducible sensor-chip replacement, has very low sample-volume requirements, and allows for individual or common addressing of all chips in the sample cell. We demonstrate the functionality of our microcantilever sensor system with a setup that can monitor eight cantilevers from four different sensor chips simultaneously.
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Rev. Sci. Instrum. 80, 093701 (2009); http://dx.doi.org/10.1063/1.3194048 (11 pages) Online Publication Date: 3 September 2009
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In an atomic force microscope (AFM), the force is normally sensed by measuring the deflection of a cantilever by an optical lever technique. Experimental results show a nonlinear relationship between the detected signal and the actual deflection of the cantilever, which is widely ignored in literature. In this study we have designed experiments to investigate different possible reasons for this nonlinearity and compared the experimental findings with calculations. It is commonly assumed that this nonlinearity only causes problems for extremely large cantilever deflections. However, our results show that the nonlinear detector response might influence many AFM studies where soft or short cantilevers are used. Based on our analysis we draw conclusions of the main reason for the nonlinearity and suggest a rule of thumb for which cantilevers one should use under different experimental conditions.
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Thermal conductivity measurement from 30 to 750 K: the 3ω method Rev. Sci. Instrum. 61, 802 (1990); http://dx.doi.org/10.1063/1.1141498 (7 pages)
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An ac technique for measuring the thermal conductivity of dielectric solids between 30 and 750 K is described. This technique, the 3ω method, can be applied to bulk amorphous solids and crystals as well as amorphous films tens of microns thick. Errors from black‐body radiation are calculated to be less than 2% even at 1000 K. Data for a‐SiO2, Pyrex 7740, and Pyroceram 9606 are compared to results obtained by conventional techniques. |
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Rev. Sci. Instrum. 75, 2787 (2004); http://dx.doi.org/10.1063/1.1785844 (23 pages) Online Publication Date: 2 September 2004
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Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to the application of calibrated forces on—and the measurement of nanometer-level displacements of—optically trapped objects. We review progress in the development of optical trapping apparatus, including instrument design considerations, position detection schemes and calibration techniques, with an emphasis on recent advances. We conclude with a brief summary of innovative optical trapping configurations and applications. |
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Rev. Sci. Instrum. 76, 061101 (2005); http://dx.doi.org/10.1063/1.1927327 (12 pages) Online Publication Date: 26 May 2005
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Nanoelectromechanical systems (NEMS) are drawing interest from both technical and scientific communities. These are electromechanical systems, much like microelectromechanical systems, mostly operated in their resonant modes with dimensions in the deep submicron. In this size regime, they come with extremely high fundamental resonance frequencies, diminished active masses,and tolerable force constants; the quality (Q) factors of resonance are in the range Q ∼ 103–105—significantly higher than those of electrical resonant circuits. These attributes collectively make NEMS suitable for a multitude of technological applications such as ultrafast sensors, actuators, and signal processing components. Experimentally, NEMS are expected to open up investigations of phonon mediated mechanical processes and of the quantum behavior of mesoscopic mechanical systems. However, there still exist fundamental and technological challenges to NEMS optimization. In this review we shall provide a balanced introduction to NEMS by discussing the prospects and challenges in this rapidly developing field and outline an exciting emerging application, nanoelectromechanical mass detection.
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Rev. Sci. Instrum. 80, 097101 (2009); http://dx.doi.org/10.1063/1.3212562 (1 page) Online Publication Date: 4 September 2009
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Femtosecond pulse shaping using spatial light modulators Rev. Sci. Instrum. 71, 1929 (2000); http://dx.doi.org/10.1063/1.1150614 (32 pages)
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We review the field of femtosecond pulse shaping, in which Fourier synthesis methods are used to generate nearly arbitrarily shaped ultrafast optical wave forms according to user specification. An emphasis is placed on programmable pulse shaping methods based on the use of spatial light modulators. After outlining the fundamental principles of pulse shaping, we then present a detailed discussion of pulse shaping using several different types of spatial light modulators. Finally, new research directions in pulse shaping, and applications of pulse shaping to optical communications, biomedical optical imaging, high power laser amplifiers, quantum control, and laser-electron beam interactions are reviewed. © 2000 American Institute of Physics. |
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Rev. Sci. Instrum. 80, 083705 (2009); http://dx.doi.org/10.1063/1.3212670 (3 pages) Online Publication Date: 31 August 2009
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We have developed a wideband digital frequency detector for high-speed frequency modulation atomic force microscopy (FM-AFM). We used a subtraction-based phase comparator (PC) in a phase-locked loop circuit instead of a commonly used multiplication-based PC, which has enhanced the detection bandwidth to 100 kHz. The quantitative analysis of the noise performance revealed that the internal noise from the developed detector is small enough to provide the theoretically limited noise performance in FM-AFM experiments in liquid. FM-AFM imaging of mica in liquid was performed with the developed detector, showing its stability and applicability to true atomic-resolution imaging in liquid.
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Rev. Sci. Instrum. 80, 084301 (2009); http://dx.doi.org/10.1063/1.3194046 (6 pages) Online Publication Date: 10 August 2009
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We describe the realization of an atomic force microscope architecture designed to perform customizable experiments in a flexible and automatic way. Novel technological contributions are given by the software implementation platform (RTAI-LINUX), which is free and open source, and from a functional point of view, by the implementation of hard real-time control algorithms. Some other technical solutions such as a new way to estimate the optical lever constant are described as well. The adoption of this architecture provides many degrees of freedom in the device behavior and, furthermore, allows one to obtain a flexible experimental instrument at a relatively low cost. In particular, we show how such a system has been employed to obtain measures in sophisticated single-molecule force spectroscopy experiments [
Fernandez and Li, Science 303, 1674 (2004)
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Calibration of atomic‐force microscope tips Rev. Sci. Instrum. 64, 1868 (1993); http://dx.doi.org/10.1063/1.1143970 (6 pages)
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Images and force measurements taken by an atomic‐force microscope (AFM) depend greatly on the properties of the spring and tip used to probe the sample’s surface. In this article, we describe a simple, nondestructive procedure for measuring the force constant, resonant frequency, and quality factor of an AFM cantilever spring and the effective radius of curvature of an AFM tip. Our procedure uses the AFM itself and does not require additional equipment. |
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Holders for in situ treatments of scanning tunneling microscopy tips Rev. Sci. Instrum. 80, 093703 (2009); http://dx.doi.org/10.1063/1.3223974 (4 pages) Online Publication Date: 15 September 2009
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We have developed holders for scanning tunneling microscopy tips that can be used for in situ treatments of the tips, such as electron bombardment (EB) heating, ion sputtering, and the coating of magnetic materials. The holders can be readily installed into the transfer paths and do not require any special type of base stages. Scanning electron microscopy is used to characterize the tip apex after EB heating. Also, spin-polarized scanning tunneling spectroscopy using an Fe coated W tip on the Cr(001) single crystal surface is performed in order to confirm both the capability of heating a tip up to about 2200 K and the spin sensitivity of the magnetically coated tip.
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Combined holographic-mechanical optical tweezers: Construction, optimization, and calibration Rev. Sci. Instrum. 80, 083703 (2009); http://dx.doi.org/10.1063/1.3196181 (7 pages) Online Publication Date: 26 August 2009
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A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers setup. This provides great flexibility as the SLM creates an array of traps, which can be moved smoothly and quickly with the GMM. To optimize performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45°, smaller angles give a full 2π phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method.
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Time‐of‐Flight Mass Spectrometer with Improved Resolution Rev. Sci. Instrum. 26, 1150 (1955); http://dx.doi.org/10.1063/1.1715212 (8 pages) Online Publication Date: 29 December 2004
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A new type of ion gun is described which greatly improves the resolution of a nonmagnetic time‐of‐flight mass spectrometer. The focusing action of this gun is discussed and analyzed mathematically. The validity of the analysis and the practicability of the gun are demonstrated by the spectra obtained. The spectrometer is capable of measuring the relative abundance of adjacent masses well beyond 100 amu. |
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Thermoelectric properties and efficiency measurements under large temperature differences Rev. Sci. Instrum. 80, 093901 (2009); http://dx.doi.org/10.1063/1.3212668 (7 pages) Online Publication Date: 1 September 2009
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The maximum efficiency of a thermoelectric generator is determined by the material’s dimensionless figure of merit ZT. Real thermoelectric material properties are highly temperature dependent and are often measured individually using multiple measurement tools on different samples. As a result, reported ZT values have large uncertainties. In this work we present an experimental technique that eliminates some of these uncertainties. We measure the Seebeck coefficient, electrical conductivity, and thermal conductivity of a single element or leg, as well as the conversion efficiency, under a large temperature difference of 2–160 °C. The advantages of this technique include (1) the thermoelectric leg is mounted only once and all measurements are in the same direction and (2) the measured properties are corroborated by efficiency measurements. The directly measured power and efficiency are compared to the values calculated from the measured properties and agree within 0.4% and 2%, respectively. The realistic testing conditions of this technique make it ideal for material characterization prior to implementation in a real thermoelectric generator.
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A simple ac bridge for detecting small resistance change Rev. Sci. Instrum. 80, 086104 (2009); http://dx.doi.org/10.1063/1.3202284 (2 pages) Online Publication Date: 18 August 2009
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A simple ac resistance bridge is proposed. The stability of the design is better than 10−6, which is especially suitable for detecting tiny changes of resistance. An example of magnetoresistance measurement for a 220 nm Au film shows the good performance of the bridge.
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