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Jun 2007

Volume 78, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 78, 061301 (2007); http://dx.doi.org/10.1063/1.2738946 (9 pages)

Thomas Beechem, Samuel Graham, Sean P. Kearney, Leslie M. Phinney, and Justin R. Serrano
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Invited Article: Simultaneous mapping of temperature and stress in microdevices using micro-Raman spectroscopy

Thomas Beechem, Samuel Graham, Sean P. Kearney, Leslie M. Phinney, and Justin R. Serrano

Rev. Sci. Instrum. 78, 061301 (2007); http://dx.doi.org/10.1063/1.2738946 (9 pages) | Cited 20 times

Online Publication Date: 11 June 2007

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Analysis of the Raman Stokes peak position and its shift has been frequently used to estimate either temperature or stress in microelectronics and microelectromechanical system devices. However, if both fields are evolving simultaneously, the Stokes shift represents a convolution of these effects, making it difficult to measure either quantity accurately. By using the relative independence of the Stokes linewidth to applied stress, it is possible to deconvolve the signal into an estimation of both temperature and stress. Using this property, a method is presented whereby the temperature and stress were simultaneously measured in doped polysilicon microheaters. A data collection and analysis method was developed to reduce the uncertainty in the measured stresses resulting in an accuracy of ±40 MPa for an average applied stress of −325 MPa and temperature of 520 °C. Measurement results were compared to three-dimensional finite-element analysis of the microheaters and were shown to be in excellent agreement. This analysis shows that Raman spectroscopy has the potential to measure both evolving temperature and stress fields in devices using a single optical measurement.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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Transient two-dimensional IR spectrometer for probing nanosecond temperature-jump kinetics

Hoi Sung Chung, Munira Khalil, Adam W. Smith, and Andrei Tokmakoff

Rev. Sci. Instrum. 78, 063101 (2007); http://dx.doi.org/10.1063/1.2743168 (10 pages) | Cited 10 times

Online Publication Date: 1 June 2007

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We have developed a Fourier transform two-dimensional infrared (2D IR) spectrometer to probe chemical reactions and biophysical processes triggered by a nanosecond temperature jump (T jump). The technical challenges for such a spectrometer involve (1) synchronization of a nanosecond T-jump laser and femtosecond laser system, (2) overcoming the decreased signal-to-noise ratio from low repetition rate data acquisition, and (3) performing an interferometric measurement through a sample with a density and index of refraction that varies with time delay after the T jump. The first challenge was overcome by synchronizing the two lasers to a clock derived from the Ti:sapphire oscillator, leading to timing accuracy of 2 ns for delays up to 50 ms. The data collection time is reduced by using undersampling with the improved signal-to-noise ratio obtained from a balanced detection scheme with a dual stripe array detector. Transient dispersed vibrational echo and 2D IR spectroscopy are applied to N-methylacetamide and ubiquitin, as examples, and the spectral responses by a temperature elevation and by structural changes of the protein are compared. The synchronization of 2D IR spectroscopy with a nanosecond temperature jump without losing its sensitivity at a low repetition rate opens a new applicability of the nonlinear spectroscopy to probe a variety of molecular structure changes induced by a nanosecond perturbation.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
82.80.Dx Analytical methods involving electronic spectroscopy
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

Optical extinction monitor using cw cavity enhanced detection

Paul L. Kebabian, Wade A. Robinson, and Andrew Freedman

Rev. Sci. Instrum. 78, 063102 (2007); http://dx.doi.org/10.1063/1.2744223 (9 pages) | Cited 6 times

Online Publication Date: 1 June 2007

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We present details of an apparatus capable of measuring optical extinction (i.e., scattering and/or absorption) with high precision and sensitivity. The apparatus employs one variant of cavity enhanced detection, specifically cavity attenuated phase shift spectroscopy, using a near-confocal arrangement of two high reflectivity (R ∼ 0.9999) mirrors in tandem with an enclosed cell 26 cm in length, a light emitting diode (LED), and a vacuum photodiode detector. The square wave modulated light from the LED passes through the absorption cell and is detected as a distorted wave form which is characterized by a phase shift with respect to the initial modulation. The amount of that phase shift is a function of fixed instrument properties—cell length, mirror reflectivity, and modulation frequency—and of the presence of a scatterer or absorber (air, particles, trace gases, etc.) within the cell. The specific implementation reported here employs a blue LED; the wavelength and spectral bandpass of the measurement are defined by the use of an interference filter centered at 440 nm with a 20 nm wide bandpass. The monitor is enclosed within a standard 19 in. rack-mounted instrumentation box, weighs 10 kg, and uses 70 W of electrical power including a vacuum pump. Measurements of the phase shift induced by Rayleigh scattering from several gases (which range in extinction coefficient from 0.4–32 Mm−1) exhibit a highly linear dependence (r2 = 0.999 97) when plotted as the cotangent of the phase shift versus the expected extinction. Using heterodyne demodulation techniques, we demonstrate a detection limit of 0.04 Mm−1 (4×10−10 cm−1) (2σ) in 10 s integration time and a base line drift of less than ±0.1 Mm−1 over a 24 h period. Detection limits decrease as the square root of integration time out to ∼ 150 s.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.60.Gz Photodetectors (including infrared and CCD detectors)
07.60.Pb Conventional optical microscopes
42.65.Es Stimulated Brillouin and Rayleigh scattering
85.60.Jb Light-emitting devices

Dynamic photolytical actinometry of the vacuum-ultraviolet radiation produced by multichannel surface discharges of submicrosecond duration

V. I. Tcheremiskine, O. P. Uteza, M. L. Sentis, and L. D. Mikheev

Rev. Sci. Instrum. 78, 063103 (2007); http://dx.doi.org/10.1063/1.2744225 (9 pages) | Cited 2 times

Online Publication Date: 4 June 2007

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Absolute measurements of the vacuum-ultraviolet (VUV) radiation power produced by a planar broadband optical source of submicrosecond light pulse duration are carried out in the transient regime of formation of a photodissociation (bleaching) wave in a photodecomposing absorptive medium. The source is based on a multichannel surface discharge initiated in Ar/N2 gas mixtures on the area of ∼ 0.1 m2. The energetic characteristics of the produced VUV radiation are determined on the basis of spatially and temporally resolved observations of the pulsed photolysis of XeF2 vapors. It is shown that the photon flux intensity produced by the source within the spectral range of 120–200 nm reaches 1.1×1023 photons/cm2 s corresponding to the effective brightness temperature of discharge plasma of 20 kK and to the intrinsic efficiency of the discharge VUV emission of 3.2%. Numerical simulations of the photolysis process show a rather weak sensitivity of the results to the fraction of discharge radiation emitted into the line spectrum, as well as to the angular distribution of emitted radiation. The spectral band of measurements can be selected according to the choice of parent photodecomposing particles.
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07.60.Dq Photometers, radiometers, and colorimeters
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.72.Bj Visible and ultraviolet sources
52.80.-s Electric discharges
82.50.-m Photochemistry
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Differential mode excitation photoacoustic spectroscopy: A new photoacoustic detection scheme

J. M. Rey and M. W. Sigrist

Rev. Sci. Instrum. 78, 063104 (2007); http://dx.doi.org/10.1063/1.2746817 (5 pages) | Cited 3 times

Online Publication Date: 7 June 2007

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A robust and simple gas sensor based on a novel photoacoustic scheme named “differential mode excitation photoacoustic spectroscopy (DME-PAS)” is presented. This method takes advantage of the selective excitation of two different modes in a resonant photoacoustic cell. A blackbody light source is used for simplicity in combination with optical correlation to provide a good selectivity. The frequency response of the proposed resonant cell is modeled using the extended Helmholtz resonator theory. The DME-PAS device is tested using acetone vapor and a model developed to describe its response when the gas concentration is varied. The obtained limit of detection is 25 ppm m−1 for acetone in room air. Using DME-PAS, the derived gas concentration is affected neither by intensity fluctuations of the light source nor by any microphone drifts.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.-d Chemical analysis and related physical methods of analysis
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators

Operation of silicon single photon avalanche diodes at cryogenic temperature

Ivan Rech, Ivan Labanca, Giacomo Armellini, Angelo Gulinatti, Massimo Ghioni, and Sergio Cova

Rev. Sci. Instrum. 78, 063105 (2007); http://dx.doi.org/10.1063/1.2743167 (3 pages) | Cited 4 times

Online Publication Date: 12 June 2007

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This article reports a complete characterization of single photon avalanche diodes (SPADs) at temperatures down to 120 K. We show that deep cooling of the device by means of a compact liquid-nitrogen Dewar brings several advantages, such as extremely low dark counting rates (down to 1 counts/s), better time resolution, and higher quantum efficiency in the visible range. By using a special current pick-off circuit, we achieved a time resolution of 20 ps full width at half maximum at 120 K for a 50 μm diameter SPAD. Afterpulsing effects are avoided by using a sufficiently long hold-off time (microseconds).
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Kk Junction diodes

Quantitative extraction of spectral line intensities and widths from x-ray spectra recorded with gated microchannel plate detectors

Greg Dunham, J. E. Bailey, G. A. Rochau, P. W. Lake, and L. B. Nielsen-Weber

Rev. Sci. Instrum. 78, 063106 (2007); http://dx.doi.org/10.1063/1.2748674 (6 pages) | Cited 3 times

Online Publication Date: 27 June 2007

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Plasma spectroscopy requires determination of spectral line intensities and widths. At Sandia National Laboratories Z facility we use elliptical crystal spectrometers equipped with gated microchannel plate detectors to record time and space resolved spectra. We collect a large volume of data typically consisting of five to six snapshots in time and five to ten spectral lines with 30 spatial elements per frame, totaling to more than 900 measurements per experiment. This large volume of data requires efficiency in processing. We have addressed this challenge by using a line fitting routine to automatically fit each spectrum using assumed line profiles and taking into account photoelectron statistics to efficiently extract line intensities and widths with uncertainties. We verified that the random data noise obeys Poisson statistics. Rescale factors for converting film exposure to effective counts required for understanding the photoelectron statistics are presented. An example of the application of these results to the analysis of spectra recorded in Z experiments is presented.
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52.70.La X-ray and γ-ray measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
07.85.Nc X-ray and γ-ray spectrometers
05.40.Ca Noise
02.50.Ng Distribution theory and Monte Carlo studies
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Detection of charged particles with charge injection devices

Kurtis A. Fletcher, Benjamin Apker, Samantha Hammond, John Punaro, Frederic J. Marshall, Jonathan Laine, and Robert Forties

Rev. Sci. Instrum. 78, 063301 (2007); http://dx.doi.org/10.1063/1.2745234 (4 pages) | Cited 1 time

Online Publication Date: 19 June 2007

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A method for using charge injection devices (CIDs) for detection of high-energy charged particles from inertial-confinement fusion reactions is described. Because of the relatively small depletion region of the CID camera (depletion depth of ∼ 7 μm), aluminum foils are placed in front of the device to reduce the energy of the charged particles and maximize the energy deposited in the CID. Simultaneous measurements of 2H(d,p)3H protons with a CID and a surface barrier detector indicate that the CID is an efficient detector of charged fusion products. Tests using high energy alpha particles emitted from a radium-226 source are also reported.
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52.70.Nc Particle measurements
52.57.Kk Fast ignition of compressed fusion fuels
52.50.Lp Plasma production and heating by shock waves and compression
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
28.52.Lf Components and instrumentation
25.45.Hi Transfer reactions
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Design and construction of uniform glow discharge plasma system operating under atmospheric condition

C. Koçum and H. Ayhan

Rev. Sci. Instrum. 78, 063501 (2007); http://dx.doi.org/10.1063/1.2745230 (5 pages) | Cited 6 times

Online Publication Date: 4 June 2007

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The design of a uniform glow discharge plasma system operating without vacuum is presented. A full-bridge switching circuit was used to switch the transformers. The primary windings of transformers were connected in parallel, but in opposite phase to double the output voltage. Theoretically, 20 000 Vpp was obtained. Rectangle copper electrodes were used, and placed parallel to each other. To prevent the spark production that is, to obtain uniformity, two 2 mm Teflon sheets were glued to the electrodes. However, it was observed that the operating frequency also affected the uniformity. For the system presented here, the frequency at which more uniformity was obtained was found to be 14 kHz.
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52.80.Hc Glow; corona
52.50.Dg Plasma sources
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
84.30.Jc Power electronics; power supply circuits

Reconstruction method of local density fluctuation for heavy ion beam probe measurements

H. Nakano, A. Fujisawa, A. Shimizu, S. Ohshima, H. Iguchi, Y. Yoshimura, and T. Minami

Rev. Sci. Instrum. 78, 063502 (2007); http://dx.doi.org/10.1063/1.2745233 (7 pages) | Cited 3 times

Online Publication Date: 12 June 2007

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Heavy ion beam probe (HIBP) is an excellent diagnostic to measure the density and potential fluctuations simultaneously in magnetically confined plasmas. However, it has been well known that the density fluctuation measured with the HIBP is not local but contains the fluctuations along the beam orbits. In this article, a method is proposed to evaluate local density fluctuation in the HIBP measurements by removing the well-known path integral effects. The reconstructed density fluctuation amplitude and power spectrum are shown, for example, by applying the proposed method on the density fluctuation measurement data obtained in a toroidal helical plasma, Compact Helical System.
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52.70.Nc Particle measurements
52.25.Gj Fluctuation and chaos phenomena
52.55.Jd Magnetic mirrors, gas dynamic traps
52.20.Dq Particle orbits

Experiments with planar inductive ion source meant for creation of H+ beams

J. H. Vainionpaa, T. Kalvas, S. K. Hahto, and J. Reijonen

Rev. Sci. Instrum. 78, 063503 (2007); http://dx.doi.org/10.1063/1.2742624 (4 pages) | Cited 5 times

Online Publication Date: 19 June 2007

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In this article the effects of different engineering parameters of rf-driven ion sources with an external spiral antenna and a quartz rf window are studied. This article consists of three main topics: the effect of source geometry on the operation gas pressure, the effect of source materials and magnetic confinement on extracted current density and ion species, and the effect of different antenna geometries on the extracted current density. The effect of source geometry was studied using three cylindrical plasma chambers with different inner diameters. The chamber materials were studied using two materials, aluminum (Al) and alumina (Al2O3). The removable 14 magnet multicusp confinement arrangement enabled us to compare the effects of the two wall materials with and without the magnetic confinement. The highest measured proton fractions were measured using Al2O3 plasma chamber and no multicusp confinement. For the compared ion sources the source with multicusp confinement and Al2O3 plasma chamber yields the highest current densities. Multicusp confinement increased the maximum extracted current by up to a factor of 2. Plasma production with different antenna geometries were also studied. The highest current density was achieved using 4.5 loop solenoid antenna with 6.0 cm diameter. A slightly lower current density with lower pressure was achieved using a tightly wound 3 loop spiral antenna with 3.3 cm inner diameter and 6 cm outer diameter.
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29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors
52.50.Dg Plasma sources
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps
52.25.Fi Transport properties

Development of advanced x-ray imaging crystal spectrometer utilizing a large area segmented proportional counter for KSTAR

S. G. Lee, J. G. Bak, U. W. Nam, M. K. Moon, and J. K. Cheon

Rev. Sci. Instrum. 78, 063504 (2007); http://dx.doi.org/10.1063/1.2749441 (4 pages) | Cited 4 times

Online Publication Date: 27 June 2007

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An advanced x-ray imaging crystal spectrometer (XICS) for KSTAR tokamak has been developed by utilizing a segmented two dimensional (2D) position-sensitive multiwire proportional counter. The XICS for the KSTAR tokamak provides time-resolved measurements of the radial ion and electron temperature profiles, toroidal plasma rotation velocity, and ionization equilibrium. The segmented 2D detector with delay-line readout and supporting electronics has been adopted to improve the photon count rate capability. The current fabrication status of the XICS for the KSTAR tokamak and the first performance test results of the prototype segmented 2D detector are presented.
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07.85.Nc X-ray and γ-ray spectrometers
52.70.La X-ray and γ-ray measurements
52.55.Fa Tokamaks, spherical tokamaks
52.25.Jm Ionization of plasmas
52.30.-q Plasma dynamics and flow
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
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Cantilever spring constant calibration using laser Doppler vibrometry

Benjamin Ohler

Rev. Sci. Instrum. 78, 063701 (2007); http://dx.doi.org/10.1063/1.2743272 (5 pages) | Cited 25 times

Online Publication Date: 5 June 2007

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Uncertainty in cantilever spring constants is a critical issue in atomic force microscopy (AFM) force measurements. Though numerous methods exist for calibrating cantilever spring constants, the accuracy of these methods can be limited by both the physical models themselves as well as uncertainties in their experimental implementation. Here we report the results from two of the most common calibration methods, the thermal tune method and the Sader method. These were implemented on a standard AFM system as well as using laser Doppler vibrometry (LDV). Using LDV eliminates some uncertainties associated with optical lever detection on an AFM. It also offers considerably higher signal to noise deflection measurements. We find that AFM and LDV result in similar uncertainty in the calibrated spring constants, about 5%, using either the thermal tune or Sader methods provided that certain limitations of the methods and instrumentation are observed.
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06.20.fb Standards and calibration
07.10.-h Mechanical instruments and equipment
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
07.79.Lh Atomic force microscopes

Atomic-force-microscope-compatible near-field scanning microwave microscope with separated excitation and sensing probes

K. Lai, M. B. Ji, N. Leindecker, M. A. Kelly, and Z. X. Shen

Rev. Sci. Instrum. 78, 063702 (2007); http://dx.doi.org/10.1063/1.2746768 (5 pages) | Cited 9 times

Online Publication Date: 7 June 2007

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We present the design and experimental results of a near-field scanning microwave microscope working at a frequency of 1 GHz. Our microscope is unique in that the sensing probe is separated from the excitation electrode to significantly suppress the common-mode signal. Coplanar waveguides were patterned onto a silicon nitride cantilever interchangeable with atomic force microscope tips, which are robust for high speed scanning. In the contact mode that we are currently using, the numerical analysis shows that contrast comes from both the variation in local dielectric properties and the sample topography. Our microscope demonstrates the ability to achieve high resolution microwave images on buried structures, as well as nanoparticles, nanowires, and biological samples.
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07.79.Lh Atomic force microscopes
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
84.40.Az Waveguides, transmission lines, striplines

Design of a scanning probe microscope with advanced sample treatment capabilities: An atomic force microscope combined with a miniaturized inductively coupled plasma source

Markus Hund and Hans Herold

Rev. Sci. Instrum. 78, 063703 (2007); http://dx.doi.org/10.1063/1.2742623 (6 pages) | Cited 3 times

Online Publication Date: 11 June 2007

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We describe the design and performance of an atomic force microscope (AFM) combined with a miniaturized inductively coupled plasma source working at a radio frequency of 27.12 MHz. State-of-the-art scanning probe microscopes (SPMs) have limited in situ sample treatment capabilities. Aggressive treatments such as plasma etching or harsh treatments such as etching in aggressive liquids typically require the removal of the sample from the microscope. Consequently, time consuming procedures are required if the same sample spot has to be imaged after successive processing steps. We have developed a first prototype of a SPM which features a quasi in situ sample treatment using a modified commercial atomic force microscope. A sample holder is positioned in a special reactor chamber; the AFM tip can be retracted by several millimeters so that the chamber can be closed for a treatment procedure. Most importantly, after the treatment, the tip is moved back to the sample with a lateral drift per process step in the 20 nm regime. The performance of the prototype is characterized by consecutive plasma etching of a nanostructured polymer film.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
52.50.Dg Plasma sources
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Calibrating a tuning fork for use as a scanning probe microscope force sensor

Yexian Qin and R. Reifenberger

Rev. Sci. Instrum. 78, 063704 (2007); http://dx.doi.org/10.1063/1.2743166 (7 pages) | Cited 8 times

Online Publication Date: 13 June 2007

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Quartz tuning forks mounted with sharp tips provide an alternate method to silicon microcantilevers for probing the tip-substrate interaction in scanning probe microscopy. The high quality factor and stable resonant frequency of the tuning fork allow accurate measurements of small shifts in the resonant frequency as the tip approaches the substrate. To permit an accurate measure of surface interaction forces, the electrical and piezoelectromechanical properties of a tuning fork have been characterized using a fiber optical interferometer.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Pz Instruments for strain, force, and torque
07.79.-v Scanning probe microscopes and components
06.20.fb Standards and calibration
77.65.-j Piezoelectricity and electromechanical effects

Practical error estimation in zoom-in and truncated tomography reconstructions

Xianghui Xiao, Francesco De Carlo, and Stuart Stock

Rev. Sci. Instrum. 78, 063705 (2007); http://dx.doi.org/10.1063/1.2744224 (7 pages) | Cited 4 times

Online Publication Date: 13 June 2007

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Synchrotron-based microtomography provides high resolution, but the resolution in large samples is often limited by the detector field of view and the pixel size. For some samples, only a small region of interest is relevant and local tomography is a powerful approach for retaining high resolution. Two methods are truncated tomography and zoom-in tomography. In this article we use existing theoretical results to estimate the error present in truncated and zoom-in tomographic reconstructions. These errors agree with the errors calculated from exact tomographic reconstructions. We argue in a heuristic manner why zoom-in tomography is superior to the truncated tomography in terms of the reconstruction error. However, the theoretical formula is not usable in practice because it requires the complete high-resolution reconstruction to be known. To solve this problem we proposed a practical method for estimating the error in zoom-in and truncated tomographies. The results using this estimation method are in very good agreement with our experimental results.
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87.59.bd Computed radiography
07.85.-m X- and γ-ray instruments
02.50.-r Probability theory, stochastic processes, and statistics

Two color, low intensity photocurrent feedback for local photocurrent spectroscopy

W. Brezna, G. Strasser, and J. Smoliner

Rev. Sci. Instrum. 78, 063706 (2007); http://dx.doi.org/10.1063/1.2745240 (4 pages)

Online Publication Date: 15 June 2007

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In this work, we introduce a two color, low intensity photocurrent feedback method for photocurrent spectroscopy utilizing an atomic force microscope (AFM). In most applications, measurements with weak optical excitations are not feasible with an AFM because the powerful AFM feedback laser severely disturbs the measurements. Therefore, we have developed a feedback system based on the pressure dependent Schottky barrier height at the tip-sample interface. The versatility of the new feedback system is demonstrated by recording high resolution photocurrent spectra on GaAs/InAs heterostructures.
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68.37.Ps Atomic force microscopy (AFM)
72.40.+w Photoconduction and photovoltaic effects
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures

Easy and direct method for calibrating atomic force microscopy lateral force measurements

Wenhua Liu, Keith Bonin, and Martin Guthold

Rev. Sci. Instrum. 78, 063707 (2007); http://dx.doi.org/10.1063/1.2745733 (7 pages) | Cited 12 times

Online Publication Date: 15 June 2007

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We have designed and tested a new, inexpensive, easy-to-make and easy-to-use calibration standard for atomic force microscopy (AFM) lateral force measurements. This new standard simply consists of a small glass fiber of known dimensions and Young’s modulus, which is fixed at one end to a substrate and which can be bent laterally with the AFM tip at the other end. This standard has equal or less error than the commonly used method of using beam mechanics to determine a cantilever’s lateral force constant. It is transferable, thus providing a universal tool for comparing the calibrations of different instruments. It does not require knowledge of the cantilever dimensions and composition or its tip height. This standard also allows direct conversion of the photodiode signal to force and, thus, circumvents the requirement for a sensor response (sensitivity) measurement.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
07.10.Pz Instruments for strain, force, and torque

Direct measurement of cantilever spring constants and correction for cantilever irregularities using an instrumented indenter

Z. Charles Ying, Mark G. Reitsma, and Richard S. Gates

Rev. Sci. Instrum. 78, 063708 (2007); http://dx.doi.org/10.1063/1.2747095 (7 pages) | Cited 7 times

Online Publication Date: 25 June 2007

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A method is presented that allows direct measurement of a wide range of spring constants of cantilevers using an indentation instrument with an integrated optical microscope. An uncertainty of less than 10% can be achieved for spring constants from 0.1 to 102 N/m. The technique makes it possible to measure the spring constant at any desired location on a cantilever of any shape, particularly at the tip location of an atomic force microscopy cantilever. The article also demonstrates a technique to detect and correct apparent length anomalies of cantilevers by analyzing spring constants at multiple positions.
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07.79.Lh Atomic force microscopes
07.10.-h Mechanical instruments and equipment

Resonator combined with a piezoelectric actuator for chemical analysis by force microscopy

Yusuke Kawai, Takahito Ono, Masayoshi Esashi, Ernst Meyer, and Christoph Gerber

Rev. Sci. Instrum. 78, 063709 (2007); http://dx.doi.org/10.1063/1.2748394 (4 pages) | Cited 4 times

Online Publication Date: 27 June 2007

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A high frequency silicon resonator for dynamic scanning force microscopy is combined with an integrated piezoelectric actuation element for large displacements. A high resonance frequency is required for imaging on the nanometer scale, and a large displacement is needed for the chemical analysis of the material at the end of the probe. The small piezoelectric resonator is formed at the end of a long piezoelectric actuator using a silicon micromachining technology. The resonator can be oscillated at 96.4 kHz, and the actuator generates a maximum displacement of 15 μm at the end of the probe. The dynamic-mode scanning force microscopy capability, using the integrated piezoelectric resonator, is demonstrated on a 2 μm pitch Au grating.
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07.10.Cm Micromechanical devices and systems
07.79.Lh Atomic force microscopes
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Aberration-corrected multipole Wien filter for energy-filtered x-ray photoemission electron microscopy

Hironobu Niimi, Wang-Jae Chun, Shushi Suzuki, Kiyotaka Asakura, and Makoto Kato

Rev. Sci. Instrum. 78, 063710 (2007); http://dx.doi.org/10.1063/1.2749449 (8 pages) | Cited 3 times

Online Publication Date: 29 June 2007

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The aberration of a multipole Wien filter for energy-filtered x-ray photoemission electron microscopy was analyzed and the optimized Fourier components of the electric and magnetic fields for the third-order aperture aberration corrections were obtained. It was found that the third-order aperture aberration correction requires 12 electrodes and magnetic poles.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
41.85.-p Beam optics
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Filtered cathodic arc deposition with ion-species-selective bias

André Anders, Nitisak Pasaja, and Sakon Sansongsiri

Rev. Sci. Instrum. 78, 063901 (2007); http://dx.doi.org/10.1063/1.2745229 (5 pages) | Cited 7 times

Online Publication Date: 5 June 2007

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A dual-cathode arc plasma source was combined with a computer-controlled bias amplifier to synchronize substrate bias with the pulsed production of plasma. In this way, bias can be applied in a material-selective way. The principle has been applied to the synthesis of metal-doped diamondlike carbon films, where the bias was applied and adjusted when the carbon plasma was condensing and the substrate was at ground when the metal was incorporated. In doing so, excessive sputtering by energetic metal ions can be avoided while the sp3/sp2 ratio can be adjusted. It is shown that the resistivity of the film can be tuned by this species-selective bias; Raman spectroscopy was used to confirm expected changes of the amorphous ta-C:Mo films. The species-selective bias principle could be extended to multiple material plasma sources and complex materials.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.50.Dg Plasma sources
52.77.Dq Plasma-based ion implantation and deposition
81.05.U- Carbon/carbon-based materials
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth

Development of a parallel-plate avalanche counter to perform conversion electron Mössbauer spectroscopy at low temperatures

Roberto Mantovan and Marco Fanciulli

Rev. Sci. Instrum. 78, 063902 (2007); http://dx.doi.org/10.1063/1.2745654 (5 pages) | Cited 7 times

Online Publication Date: 6 June 2007

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We describe an experimental setup based on a sealed parallel-plate avalanche counter, which allows conversion electron Mössbauer spectroscopy at temperatures down to 120 K. A study of the counting gas performances is carried out in order to find out the appropriate operating conditions. The detector can work in a wide range of pressures and voltages at room and low temperatures, for both iron- and tin-based Mössbauer transitions. An estimation of the gas gain is obtained by using a simple approach, which considers the avalanche gas process in parallel-plate geometry. The gas gain as a function of the filling pressure shows a maximum at room temperature and a monotonic increase at low temperature. The experimental setup has been tested with the determination of the Debye temperature of β-Sn, SnO2, and ε-FeSi.
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76.80.+y Mössbauer effect; other γ-ray spectroscopy
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
29.40.-n Radiation detectors
07.85.Nc X-ray and γ-ray spectrometers

Experimental investigation of dynamic effects in a two-bar/three-point bend fracture test

Fengchun Jiang and Kenneth S. Vecchio

Rev. Sci. Instrum. 78, 063903 (2007); http://dx.doi.org/10.1063/1.2746630 (12 pages) | Cited 6 times

Online Publication Date: 22 June 2007

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A Hopkinson pressure bar has been modified to measure the dynamic fracture properties of materials at loading rates greater than ∼ 106 MPa math/s. Some fundamental dynamic effects associated with the incident stress pulse, such as stress wave propagation characteristics along the Hopkinson bar and within the cracked specimen, the specimen’s dynamic response excited by the stress pulse, and the specimen contact situations with the impactor and supports, need to be understood. To better comprehend these fundamental issues, an experimental investigation of these dynamic effects with the emphasis on “loss of contact” was first performed on a two-bar/three-point dynamic bend fracture test setup using a voltage measurement circuit across the specimen/loading-pin interfaces and high-speed photographs. It was demonstrated here that the three-point bend specimen employed with the current two-bar/three-point bend test setup remains in contact with the impactor and supports throughout the first loading duration and that “loss of contact” does not occur. A further improvement using a pulse-shaping technique was employed for achieving a tailored incident pulse. The effect of pulse shaper on the rise time and duration of the incident pulse as well as the dynamic stress equilibrium in the cracked three-point bend has been investigated, for the first time here, with profound implications for significantly improved dynamic three-point bend fracture testing.
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81.70.Bt Mechanical testing, impact tests, static and dynamic loads
07.10.Pz Instruments for strain, force, and torque
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