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Top 20 Most Read Articles
June 2008
The 20 articles with the most full-text downloads during the month, in descending order.
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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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Rev. Sci. Instrum. 79, 051301 (2008); http://dx.doi.org/10.1063/1.2919944 (12 pages) Online Publication Date: 12 May 2008
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We review the techniques used in the design and construction of cryogenic sapphire oscillators at the University of Western Australia over the 18 year history of the project. We describe the project from its beginnings when sapphire oscillators were first developed as low-noise transducers for gravitational wave detection. Specifically, we describe the techniques that were applied to the construction of an interrogation oscillator for the PHARAO Cs atomic clock in CNES, in Toulouse France, and to the 2006 construction of four high performance oscillators for use at NMIJ and NICT, in Japan, as well as a permanent secondary frequency standard for the laboratory at UWA. Fractional-frequency fluctuations below 6×10−16 at integration times between 10 and 200 s have been repeatedly achieved.
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A high voltage programmable ramp generator Rev. Sci. Instrum. 79, 054701 (2008); http://dx.doi.org/10.1063/1.2912823 (5 pages) Online Publication Date: 5 May 2008
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In this paper, a ramp generator with programmable slope is presented. It consists of a high voltage step generator, followed by integrator. The capacitor and inductor in the integrator are designed such that they can be varied by a microcontroller. This circuit generates two bipolar ramps with fastest speed <1 ns and provides continuous speed variation from 6 to 30 ns for a ramp of 500 V. This is being developed as a part of automated streak camera for deflection of electron beam.
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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. 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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A versatile all-optical Bose–Einstein condensates apparatus Rev. Sci. Instrum. 79, 053101 (2008); http://dx.doi.org/10.1063/1.2917405 (5 pages) Online Publication Date: 6 May 2008
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We report on the construction of an all-optical Bose–Einstein condensate apparatus by using a CO2 laser trap. We also report on measurements of the trap frequency by applying a periodic perturbation to the trap potential. The derived trap parameters agree well with the design parameters.
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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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Rev. Sci. Instrum. 68, 3477 (1997); http://dx.doi.org/10.1063/1.1148310 (8 pages)
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The application of electrostatic lenses is demonstrated to give a substantial improvement of the two-dimensional (2D) ion/electron imaging technique. This combination of ion lens optics and 2D detection makes “velocity map imaging” possible, i.e., all particles with the same initial velocity vector are mapped onto the same point on the detector. Whereas the more common application of grid electrodes leads to transmission reduction, severe trajectory deflections and blurring due to the non-point source geometry, these problems are avoided with open lens electrodes. A three-plate assembly with aperture electrodes has been tested and its properties are compared with those of grid electrodes. The photodissociation processes occurring in molecular oxygen following the two-photon 3dπ(3Σ1g−)(v = 2, N = 2)←X(3Σg−) Rydberg excitation around 225 nm are presented here to show the improvement in spatial resolution in the ion and electron images. Simulated trajectory calculations show good agreement with experiment and support the appealing properties of this velocity mapping technique. © 1997 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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Rev. Sci. Instrum. 79, 063102 (2008); http://dx.doi.org/10.1063/1.2930869 (14 pages) Online Publication Date: 5 June 2008
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We describe a momentum imaging setup for direct time-resolved studies of ionization-induced molecular dynamics. This system uses a tabletop ultrafast extreme-ultraviolet (EUV) light source based on high harmonic upconversion of a femtosecond laser. The high photon energy (around 42 eV) allows access to inner-valence states of a variety of small molecules via single photon excitation, while the sub-–10-fs pulse duration makes it possible to follow the resulting dynamics in real time. To obtain a complete picture of molecular dynamics following EUV induced photofragmentation, we apply the versatile cold target recoil ion momentum spectroscopy reaction microscope technique, which makes use of coincident three-dimensional momentum imaging of fragments resulting from photoexcitation. This system is capable of pump-probe spectroscopy by using a combination of EUV and IR laser pulses with either beam as a pump or probe pulse. We report several experiments performed using this system.
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Possible application of carbon nanotube bundles for low temperature sensing Rev. Sci. Instrum. 79, 053909 (2008); http://dx.doi.org/10.1063/1.2932343 (5 pages) Online Publication Date: 28 May 2008
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We report on the R-T measurement of carbon nanotube bundles from room temperature down to 1 K. The resistance at a particular temperature depends on the diameter of the bundle. The larger the bundle diameter is, the lower the value of the resistance. The resistance increases with the decrease in temperature as in the case of carbon, carbon glass resistance thermometer, and carbon nanotubes reported in the literature. The rate of the variation of resistance depends on the resistance of the bundle at room temperature which can be explored for the low temperature thermometry. Overall, the resistance and the sensitivity of the bundle depend on the bundle diameter which can be monitored easily. |
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A subnanosecond pulsed ion source for micrometer focused ion beams Rev. Sci. Instrum. 79, 053102 (2008); http://dx.doi.org/10.1063/1.2918136 (6 pages) Online Publication Date: 6 May 2008
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A new, compact design of an ion source delivers nanosecond pulsed ion beams with low emittance, which can be focused to micrometer size. By using a high-power, 25 fs laser pulse focused into a gas region of 10−6 mbar, ions at very low temperatures are produced in the small laser focal volume of 5 μm diameter by 20 μm length through multiphoton ionization. These ions are created in a cold environment, not in a hot plasma, and, since the ionization process itself does not significantly heat them, have as a result essentially room temperature. The generated ion pulse, up to several thousand ions per pulse, is extracted from the source volume with ion optical elements that have been carefully designed by simulation calculations. Externally triggered, its subnanosecond duration and even smaller time jitter allow it to be superimposed with other pulsed particle or laser beams. It therefore can be combined with any type of collision experiment where the size and the time structure of the projectile beam crucially affect the achievable experimental resolution.
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Gradiometric micro-SQUID susceptometer for scanning measurements of mesoscopic samples Rev. Sci. Instrum. 79, 053704 (2008); http://dx.doi.org/10.1063/1.2932341 (7 pages) Online Publication Date: 28 May 2008
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We have fabricated and characterized micro-SQUID susceptometers for use in low-temperature scanning probe microscopy systems. The design features the following: a 4.6 μm diameter pickup loop; an integrated field coil to apply a local field to the sample; an additional counterwound pickup-loop/field-coil pair to cancel the background signal from the applied field in the absence of the sample; modulation coils to allow setting the SQUID at its optimum bias point (independent of the applied field), and shielding and symmetry that minimizes coupling of magnetic fields into the leads and body of the SQUID. We use a SQUID series array preamplifier to obtain a system bandwidth of 1 MHz. The flux noise at 125 mK is approximately 0.25μΦ0/
 above 10 kHz, with a value of 2.5μΦ0/ at 10 Hz. The nominal sensitivity to electron spins located at the center of the pickup loop is approximately 200μB/ above 10 kHz, in the white-noise frequency region. |
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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. 79, 033704 (2008); http://dx.doi.org/10.1063/1.2842631 (9 pages) Online Publication Date: 6 March 2008
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We present the design and first results of a low-temperature, ultrahigh vacuum scanning probe microscope enabling atomic resolution imaging in both scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM) modes. A tuning-fork-based sensor provides flexibility in selecting probe tip materials, which can be either metallic or nonmetallic. When choosing a conducting tip and sample, simultaneous STM/NC-AFM data acquisition is possible. Noticeable characteristics that distinguish this setup from similar systems providing simultaneous STM/NC-AFM capabilities are its combination of relative compactness (on-top bath cryostat needs no pit), in situ exchange of tip and sample at low temperatures, short turnaround times, modest helium consumption, and unrestricted access from dedicated flanges. The latter permits not only the optical surveillance of the tip during approach but also the direct deposition of molecules or atoms on either tip or sample while they remain cold. Atomic corrugations as low as 1 pm could successfully be resolved. In addition, lateral drifts rates of below 15 pm/h allow long-term data acquisition series and the recording of site-specific spectroscopy maps. Results obtained on Cu(111) and graphite illustrate the microscope’s performance.
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Planar nanowire arrays formed by atomic-terrace low-angle shadowing Rev. Sci. Instrum. 79, 053907 (2008); http://dx.doi.org/10.1063/1.2929835 (4 pages) Online Publication Date: 20 May 2008
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A relatively simple method for preparation of planar nanowire arrays on vicinal substrates by molecular beam epitaxy is presented. The atomic step-and-terrace morphology of vicinal substrates is used to produce a shadowing effect on a highly collimated molecular beam at an oblique incidence to the substrate. The collimation is achieved by placing the evaporation source at a large working distance (40–100 cm) from the substrate. The method’s capabilities have been demonstrated by preparation of arrays of Ag and Au nanowires on vicinal Si(111) and α-Al2O3 (0001) substrates. Nanowires with a width of down to 10–15 nm and a thickness of 1.5 nm have been readily achieved.
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Cantilever transducers as a platform for chemical and biological sensors Rev. Sci. Instrum. 75, 2229 (2004); http://dx.doi.org/10.1063/1.1763252 (25 pages) Online Publication Date: 21 June 2004
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Since the late 1980s there have been spectacular developments in micromechanical or microelectro-mechanical (MEMS) systems which have enabled the exploration of transduction modes that involve mechanical energy and are based primarily on mechanical phenomena. As a result an innovative family of chemical and biological sensors has emerged. In this article, we discuss sensors with transducers in a form of cantilevers. While MEMS represents a diverse family of designs, devices with simple cantilever configurations are especially attractive as transducers for chemical and biological sensors. The review deals with four important aspects of cantilever transducers: (i) operation principles and models; (ii) microfabrication; (iii) figures of merit; and (iv) applications of cantilever sensors. We also provide a brief analysis of historical predecessors of the modern cantilever sensors. © 2004 American Institute of Physics. |
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Calibration of rectangular atomic force microscope cantilevers Rev. Sci. Instrum. 70, 3967 (1999); http://dx.doi.org/10.1063/1.1150021 (3 pages)
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A method to determine the spring constant of a rectangular atomic force microscope cantilever is proposed that relies solely on the measurement of the resonant frequency and quality factor of the cantilever in fluid (typically air), and knowledge of its plan view dimensions. This method gives very good accuracy and improves upon the previous formulation by Sader et al. [Rev. Sci. Instrum. 66, 3789 (1995)] which, unlike the present method, requires knowledge of both the cantilever density and thickness. © 1999 American Institute of Physics. |
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Rev. Sci. Instrum. 69, 1207 (1998); http://dx.doi.org/10.1063/1.1148795 (17 pages)
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In this article, we review progress in the development of high peak-power ultrafast lasers, and discuss in detail the design issues which determine the performance of these systems. Presently, lasers capable of generating terawatt peak powers with unprecedented short pulse duration can now be built on a single optical table in a small-scale laboratory, while large-scale lasers can generate peak power of over a petawatt. This progress is made possible by the use of the chirped-pulse amplification technique, combined with the use of broad-bandwidth laser materials such as Ti:sapphire, and the development of techniques for generating and propagating very short (10–30 fs) duration light pulses. We also briefly summarize some of the new scientific advances made possible by this technology, such as the generation of coherent femtosecond x-ray pulses, and the generation of MeV-energy electron beams and high-energy ions. © 1998 American Institute of Physics. |
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Compact two-dimensional coarse-positioner for scanning probe microscopes Rev. Sci. Instrum. 79, 063701 (2008); http://dx.doi.org/10.1063/1.2940234 (3 pages) Online Publication Date: 16 June 2008
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We report on the design and fabrication of a compact two-dimensional xy-positioner for scanning probe microscopes. This positioner uses three piezoelectric bimorphs in flexing or length-change mode by appropriate selection of electrodes and voltage polarities. One end of these bimorphs is fixed to a rectangular metal frame while on each of the free ends two sapphire disks are fixed which can slide against the polished plates of a platform movable in the xy-plane. For moving the platform by one step, the bimorphs are deformed sequentially in one mode and they are brought back to their undeformed state simultaneously. The motion of the positioner has been tested with an optical microscope and a homemade scanning tunneling microscope.
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