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Top 20 Most Read Articles
September 2007
The 20 articles with the most full-text downloads during the month, in descending order.
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Rev. Sci. Instrum. 78, 081101 (2007); http://dx.doi.org/10.1063/1.2754076 (8 pages) Online Publication Date: 6 August 2007
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Cantilevers with single micro- or nanoparticle probes have been widely used for atomic force microscopy surface force measurements and apertureless scanning near-field optical microscopy applications. In this article, I critically review the particle attachment and modification techniques currently available, to help researchers choose the appropriate techniques for specific applications.
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Pre‐preionization of a long optical pulse magnetic‐spiker sustainer XeCl laser Rev. Sci. Instrum. 65, 3621 (1994); http://dx.doi.org/10.1063/1.1144482 (7 pages)
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A novel preionization technique which uses a surface corona discharge to produce preionization electrons for the controlled low jitter breakdown of a main corona‐gap preionizer is described. The pre‐preionization scheme has been used to reliably preionize a long optical pulse (450 ns full width at half‐maximum) XeCl laser. The laser excitation circuit is a new version of the overshoot mode of magnetic‐spiker sustainer excitation specifically designed to be simple, reliable, and capable of high repetition rate operation. © 1994 American Institute of Physics. |
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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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Print your atomic force microscope Rev. Sci. Instrum. 78, 075105 (2007); http://dx.doi.org/10.1063/1.2751099 (5 pages) Online Publication Date: 9 July 2007
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Progress in scanning probe microscopy profited from a flourishing multitude of new instrument designs, which lead to novel imaging modes and as a consequence to innovative microscopes. Often these designs were hampered by the restrictions, which conventional milling techniques impose. Modern rapid prototyping techniques, where layer by layer is added to the growing piece either by light driven polymerization or by three-dimensional printing techniques, overcome this constraint, allowing highly concave or even embedded and entangled structures. We have employed such a technique to manufacture an atomic force microscopy (AFM) head, and we compared its performance with a copy milled from aluminum. We tested both AFM heads for single molecule force spectroscopy applications and found little to no difference in the signal-to-noise ratio as well as in the thermal drift. The lower E modulus seems to be compensated by higher damping making this material well suited for low noise and low drift applications. Printing an AFM thus offers unparalleled freedom in the design and the rapid production of application-tailored custom instruments.
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Nanosecond delay with subpicosecond uncertainty Rev. Sci. Instrum. 78, 084701 (2007); http://dx.doi.org/10.1063/1.2760982 (5 pages) Online Publication Date: 2 August 2007
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We have combined a commercially available, variable-length coaxial delay line (trombone line) with a high-resolution linear translation system. The result is better resolution and lower uncertainty in the achievable delays than previously available. The range of delay is 0 ps to approximately 1250 ps, the bidirectional resolution is 2.0 ps, the unidirectional resolution is 0.2 ps, and the uncertainty (95% confidence interval) in the measured delay is ±0.09 ps. Drift, temperature dependence, repeatability, linearity, and hysteresis were also examined.
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Rev. Sci. Instrum. 78, 083105 (2007); http://dx.doi.org/10.1063/1.2773783 (8 pages) Online Publication Date: 23 August 2007
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An experimental setup for time- and angle-resolved photoemission spectroscopy using a femtosecond 1 kHz high harmonic light source and a two-dimensional electron analyzer for parallel energy and momentum detection is presented. A selection of the 27th harmonic (41.85 eV) from the harmonic spectrum of the light source is achieved with a multilayer Mo/Si double mirror monochromator. The extinction efficiency of the monochromator in selecting this harmonic is shown to be better than 7:1, while the transmitted bandwidth of the selected harmonic is capable of supporting temporal pulse widths as short as 3 fs. The recorded E(k) photoelectron spectrum from a Cu(111) surface demonstrates an angular resolution of better than 0.6° ( = 0.03 Å−1 at Ekin,e = 36 eV). Used in a pump-probe configuration, the described experimental setup represents a powerful experimental tool for studying the femtosecond dynamics of ultrafast surface processes in real time.
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Novel approach to Abel inversion Rev. Sci. Instrum. 78, 093701 (2007); http://dx.doi.org/10.1063/1.2777159 (5 pages) Online Publication Date: 4 September 2007
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Simple yet versatile, physically valid emissivity functions for peaked and hollow profiles with only two determinable parameters are proposed for performing Abel inversion. The advantages of the proposed functions have been explored. The inversion is very fast, accurate, convenient, and viable, in contrast to the existing methods. The validation of these functions has been confirmed by using simulated data under various conditions. The error in the process has been computed and found to depend on the functional form of the model emissivity. A comprehensive comparison has been drawn with the existing method and it has been found to offer a definite advantage over the existing technique in some respects, especially for real time applications. Limitation of this technique has also been discussed. The soft x-ray and visible light emissivity profile of SINP tokamak has been successfully obtained by using this method.
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Rev. Sci. Instrum. 78, 083104 (2007); http://dx.doi.org/10.1063/1.2774823 (5 pages) Online Publication Date: 23 August 2007
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We describe a momentum resolving time-of-flight ion mass spectrometer that combines a high mass resolution, a velocity focusing condition for improved momentum resolution, and field-free conditions in the source region for high resolution electron detection. It is used in electron-ion coincidence experiments to record multiple ionic fragments produced in breakup reactions of small to medium sized molecules, such as F3SiCH2CH2Si(CH3)3. These breakup reactions are caused by soft x rays or intense laser fields. The ion spectrometer uses pulsed extraction fields, an electrostatic lens, and a delay line detector to resolve the position. Additionally, we describe a simple analytical method for calculating the momentum from the measured hit position and the time of flight of the ions.
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Novel method for mechanical characterization of polymeric nanofibers Rev. Sci. Instrum. 78, 085108 (2007); http://dx.doi.org/10.1063/1.2771092 (7 pages) Online Publication Date: 20 August 2007
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A novel method to perform nanoscale mechanical characterization of highly deformable nanofibers has been developed. A microelectromechanical system (MEMS) test platform with an on-chip leaf-spring load cell that was tuned with the aid of a focused ion beam was built for fiber gripping and force measurement and it was actuated with an external piezoelectric transducer. Submicron scale tensile tests were performed in ambient conditions under an optical microscope. Engineering stresses and strains were obtained directly from images of the MEMS platform, by extracting the relative rigid body displacements of the device components by digital image correlation. The accuracy in determining displacements by this optical method was shown to be better than 50 nm. In the application of this method, the mechanical behavior of electrospun polyacrylonitrite nanofibers with diameters ranging from 300 to 600 nm was investigated. The stress-strain curves demonstrated an apparent elastic-perfectly plastic behavior with elastic modulus of 7.6±1.5 GPa and large irreversible strains that exceeded 220%. The large fiber stretch ratios were the result of a cascade of periodic necks that formed during cold drawing of the nanofibers.
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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. 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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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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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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Iterative image-based modeling and control for higher scanning probe microscope performance Rev. Sci. Instrum. 78, 083704 (2007); http://dx.doi.org/10.1063/1.2773534 (12 pages) Online Publication Date: 29 August 2007
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In this article, we develop an image-based approach to model and control the dynamics of scanning probe microscopes (SPMs) during high-speed operations. SPMs are key enabling tools in the experimental investigation and manipulation of nano- and subnanoscale phenomena; however, the speed at which the SPM probe can be positioned over the sample surface is limited due to adverse dynamic effects. It is noted that SPM speed can be increased using model-based control techniques. Modeling the SPM dynamics is, however, challenging because currently available sensing methods do not measure the SPM tip directly. Additionally, the resolution of currently available sensing methods is limited by noise at higher bandwidth. Our main contribution is an iterative image-based modeling method which overcomes these modeling difficulties (caused by sensing limitations). The method is applied to model an experimental scanning tunneling microscope (STM) system and to achieve high-speed imaging. Specifically, we model the STM up to a frequency of 2000 Hz (corresponds to ∼ 2/3 of the resonance frequency of our system) and achieve ∼ 1.2% error in 1 nm square images at that same frequency.
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Multiwell micromechanical cantilever array reader for biotechnology Rev. Sci. Instrum. 78, 084103 (2007); http://dx.doi.org/10.1063/1.2775433 (7 pages) Online Publication Date: 29 August 2007
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We use a multiwell micromechanical cantilever sensor (MCS) device to measure surface stress changes induced by specific adsorption of molecules. A multiplexed assay format facilitates the monitoring of the bending of 16 MCSs in parallel. The 16 MCSs are grouped within four separate wells. Each well can be addressed independently by different analyte liquids. This enables functionalization of MCS separately by flowing different solutions through each well. In addition, each well contains a fixed reference mirror which allows measuring the absolute bending of MCS. In addition, the mirror can be used to follow refractive index changes upon mixing of different solutions. The effect of the flow rate on the MCS bending change was found to be dependent on the absolute bending value of MCS. Experiments and finite element simulations of solution exchange in wells were performed. Both revealed that one solution can be exchanged by another one after 200 μl volume has flown through. Using this device, the adsorption of thiolated DNA molecules and 6-mercapto-1-hexanol on gold surfaces was performed to test the nanomechanical response of MCS.
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Rev. Sci. Instrum. 78, 093702 (2007); http://dx.doi.org/10.1063/1.2779215 (8 pages) Online Publication Date: 5 September 2007
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A number of atomic force microscopy cantilevers have been exhaustively calibrated by a number of techniques to obtain both normal and frictional force constants to evaluate the relative accuracy of the different methods. These were of either direct or indirect character—the latter relies on cantilever resonant frequencies. The so-called
Sader [Rev. Sci. Instrum. 70, 3967 (1999)
] and
Cleveland [Rev. Sci. Instrum. 64, 403 (1993)
] techniques are compared for the normal force constant calibration and while agreement was good, a systematic difference was observed. For the torsional force constants, all the techniques displayed a certain scatter but the agreement was highly encouraging. By far the simplest technique is that of Sader, and it is suggested in view of this validation that this method should be generally adopted. The issue of the photodetector calibration is also addressed since this is necessary to obtain the cantilever twist from which the torsional force is calculated. Here a technique of obtaining the torsional photodetector sensitivity by combining the direct and indirect methods is proposed. Direct calibration measurements were conducted in liquid as well as air, and a conversion factor was obtained showing that quantitative friction measurements in liquid are equally feasible provided the correct calibration is performed.
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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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Measurement of ion energy distributions using a combined energy and mass analyzer Rev. Sci. Instrum. 78, 083503 (2007); http://dx.doi.org/10.1063/1.2769352 (6 pages) Online Publication Date: 20 August 2007
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A method is described for measuring ion energy distributions using a commercially available, combined energy analyzer/mass spectrometer. The distributions were measured at an electrode located adjacent to pulsed, electron beam-generated plasmas produced in argon. The method uses energy-dependent tuning and was tested for various plasma conditions. The results indicate an improved collection efficiency of low-energy ions when compared to conventional approaches in measuring ion energy distributions.
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Rev. Sci. Instrum. 78, 091301 (2007); http://dx.doi.org/10.1063/1.2783112 (11 pages) Online Publication Date: 17 September 2007
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Originally conceived and developed at the European Synchrotron Radiation Facility (ESRF) as an “area” detector for rapid x-ray imaging studies, the fast readout low noise (FReLoN) detector of the ESRF [
J.-C. Labiche, ESRF Newsletter 25, 41 (1996)
] has been demonstrated to be a highly versatile and unique detector. Charge coupled device (CCD) cameras at present available on the public market offer either a high dynamic range or a high readout speed. A compromise between signal dynamic range and readout speed is always sought. The parameters of the commercial cameras can sometimes be tuned, in order to better fulfill the needs of specific experiments, but in general these cameras have a poor duty cycle (i.e., the signal integration time is much smaller than the readout time). In order to address scientific problems such as time resolved experiments at the ESRF, a FReLoN camera has been developed by the Instrument Support Group at ESRF. This camera is a low noise CCD camera that combines high dynamic range, high readout speed, accuracy, and improved duty cycle in a single image. In this paper, we show its application in a quasi-one-dimensional sense to dynamic problems in materials science, catalysis, and chemistry that require data acquisition on a time scale of milliseconds or a few tens of milliseconds. It is demonstrated that in this mode the FReLoN can be applied equally to the investigation of rapid changes in long range order (via diffraction) and local order (via energy dispersive extended x-ray absorption fine structure) and in situations of x-ray hardness and flux beyond the capacity of other detectors.
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Rev. Sci. Instrum. 78, 086101 (2007); http://dx.doi.org/10.1063/1.2764372 (3 pages) Online Publication Date: 7 August 2007
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A method for calibrating the stiffness of atomic force microscope (AFM) cantilevers is demonstrated using an array of uniform microfabricated reference cantilevers. A series of force-displacement curves was obtained using a commercial AFM test cantilever on the reference cantilever array, and the data were analyzed using an implied Euler-Bernoulli model to extract the test cantilever spring constant from linear regression fitting. The method offers a factor of 5 improvement over the precision of the usual reference cantilever calibration method and, when combined with the Système International traceability potential of the cantilever array, can provide very accurate spring constant calibrations.
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