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May 2000

Volume 71, Issue 5, pp. 1929-2249

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back to top MICROSCOPY and IMAGING

In situ observation of surface deformation of polymer films by atomic force microscopy

Takashi Nishino, Akiko Nozawa, Masaru Kotera, and Katsuhiko Nakamae

Rev. Sci. Instrum. 71, 2094 (2000); http://dx.doi.org/10.1063/1.1150585 (3 pages) | Cited 11 times

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The tensile X–Y stage, providing a load cell and a stretching device, has been constructed to observe the surface deformation of polymer film in situ by using an atomic force microscope (AFM). From the three-dimensional AFM images, the streak-like bumps were observed on a polyethylene terephalate (PET) film surface. By monitoring the change in the distance between them by the tensile load, the strain was evaluated in the direction both parallel and perpendicular to the tensile direction. The microscopic stress–strain relationship by AFM coincided with the macroscopic one, which indicates so-called affine deformation of PET film. Young’s modulus was obtained as 2.3 GPa for PET from the initial slope of the stress–strain curve by AFM. The apparent Poisson ratio of the PET film surface could be also evaluated. © 2000 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
61.41.+e Polymers, elastomers, and plastics
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
62.20.F- Deformation and plasticity
62.20.D- Elasticity

High-speed atomic force microscopy in liquid

T. Sulchek, R. Hsieh, J. D. Adams, S. C. Minne, C. F. Quate, and D. M. Adderton

Rev. Sci. Instrum. 71, 2097 (2000); http://dx.doi.org/10.1063/1.1150586 (3 pages) | Cited 41 times

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High-speed constant force imaging with the atomic force microscope (AFM) has been achieved in liquid. By using a standard optical lever AFM, and a cantilever with an integrated zinc oxide (ZnO) piezoelectric actuator, an imaging bandwidth of 38 kHz has been achieved; nearly 100 times faster than conventional AFMs. For typical samples, this bandwidth corresponds to tip velocities in excess of 3 mm/s. High-speed AFM imaging in liquid will (1) permit chemical and biological AFM observations to occur at speeds previously inaccessible, and (2) significantly decrease measurement times in standard AFM liquid operation. © 2000 American Institute of Physics.
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07.79.Lh Atomic force microscopes
87.64.Dz Scanning tunneling and atomic force microscopy

Construction and characterization of a heating stage for a scanning probe microscope up to 215 °C

Z. Xie, E. Z. Luo, J. B. Xu, I. H. Wilson, L. H. Zhao, and X. X. Zhang

Rev. Sci. Instrum. 71, 2100 (2000); http://dx.doi.org/10.1063/1.1150587 (4 pages) | Cited 7 times

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In this article, we present a study on construction and characterization of a heating stage compatible to commercially available scanning probe microscopes working in contact and tapping modes. Thermal properties of the heating stage have been characterized. With the heating stage, sample surface temperature can reach as high as 215 °C while the scanner temperature is kept below 125 °C. Below 50 °C, the stage temperature is very stable, with fluctuations less than 0.05 °C within half an hour. In both the contact and tapping mode of the force microscope, the image distortions have been calibrated, which occurs due to the decrease of piezoelectric coefficient at high temperature. It has been found that a cork wood spacer is excellent for thermal isolation to prevent the scanner from overheating. Examples of applications of the heating stage will be presented and discussed. © 2000 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
07.20.Hy Furnaces; heaters
back to top CONDENSED MATTER; MATERIALS

Light output measurements of the organic light-emitting devices

Yi He, Reiji Hattori, and Jerzy Kanicki

Rev. Sci. Instrum. 71, 2104 (2000); http://dx.doi.org/10.1063/1.1150588 (4 pages) | Cited 5 times

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In this article we describe a novel light output measurements method of the organic light-emitting devices (OLEDs). This method not only provides the electroluminescence (EL) spectral response of the OLEDs, but also gives the spectral distribution of the radiant power (W), luminance (cd/m2), luminous flux (lm), and photon emission of the measured light-emitting object. Also an accurate calculation method of the OLED EL external quantum efficiency is proposed. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
07.60.Dq Photometers, radiometers, and colorimeters
85.60.Gz Photodetectors (including infrared and CCD detectors)

Analysis of light scattering centers in crystals using modified light scattering tomography

K. Sakai

Rev. Sci. Instrum. 71, 2108 (2000); http://dx.doi.org/10.1063/1.1150589 (3 pages)

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Light scattering measurements using an infrared laser light and a bias light have been carried out for the first time to investigate defect energy levels in indium-doped GaAs crystals. The principle of this method is based on the analysis of scattered light intensity variation induced by the bias light. A drastic quenching effect is observed at some wavelength of the bias light. It was found that there are two kinds of light scattering centers in as-grown indium-doped GaAs crystals. © 2000 American Institute of Physics.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
71.55.Eq III-V semiconductors

Studies on molten glass sealing in diffusion coefficient measurements using shear cell technique

Jianding Yu, Makoto Natsuisaka, Hirokazu Kato, Satoshi Matsumoto, Kyoichi Kinoshita, Toshio Itami, and Shinichi Yoda

Rev. Sci. Instrum. 71, 2111 (2000); http://dx.doi.org/10.1063/1.1150590 (6 pages) | Cited 1 time

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To develop a shear cell technique for measuring the diffusion coefficient of molten materials with high vapor pressure, molten silica glass was used to seal the vapor leak from the clearance between the cell and the rotating rod. An apparatus was designed to investigate the sealing ability of several molten silica glasses. Using Corning 0211, 7059, and 7740 silica glasses, Ar could be sealed under 150 kPa in the 1100–1500 K temperature range. The corresponding viscosities of the molten silica glasses in the sealing temperature range were 105.3–103.8 Pa s. Based on the results of Ar sealing experiments, the configuration of molten glass sealing was used to seal the As vapor leak in InxGa1−xAs diffusion coefficient measurement experiments. The As vapor leak was successfully sealed and excellent diffusion coefficient measurement data were obtained using the shear cell technique during microgravity experiments carried out on sounding rocket. © 2000 American Institute of Physics.
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81.70.Ha Testing in microgravity environments
81.10.Mx Growth in microgravity environments
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Characterization of phosphosilicate thin films using confocal Raman microscopy

Manyalibo J. Matthews, Alexander L. Harris, Allan J. Bruce, and Mark J. Cardillo

Rev. Sci. Instrum. 71, 2117 (2000); http://dx.doi.org/10.1063/1.1150591 (4 pages) | Cited 5 times

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We have demonstrated a characterization tool based on confocal Raman microscopy capable of studying the vibrational spectrum of silica-on-silicon-based thin films within a confined, ∼1 μm3-size volume beneath the sample surface. The Raman spectra of a set of phosphosilicate thin film samples have been quantitatively analyzed and correlated with both phosphorus concentration CP and refractive index n, as determined by conventional methods. The normalized intensity of the P☒O vibration scaled linearly with CP and n, and allowed for the calibration of the Raman measurements to a precision of ∼0.2 wt. %P and ∼ 10−4 in index. The capability of this technique for studying index and dopant profiles in arbitrary systems is also discussed. © 2000 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
07.60.Pb Conventional optical microscopes
78.35.+c Brillouin and Rayleigh scattering; other light scattering
42.70.Ce Glasses, quartz
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Temperature stabilized effusion cell evaporation source for thin film deposition and molecular-beam epitaxy

H. F. Tiedje and D. E. Brodie

Rev. Sci. Instrum. 71, 2121 (2000); http://dx.doi.org/10.1063/1.1150592 (4 pages)

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A simple effusion cell evaporation source for thin film deposition and molecular-beam epitaxy is described. The source consists of a crucible with a thermocouple temperature sensor heated by a resistive crucible heater. Radiation heat transfer from the crucible to the thermocouple produces a consistent and reproducible thermocouple temperature for a given crucible temperature, without direct contact between the thermocouple and the crucible. The thermocouple temperature is somewhat less than the actual crucible temperature because of heat flow from the thermocouple junction along the thermocouple lead wires. In a typical case, the thermocouple temperature is 1007 °C while the crucible is at 1083 °C. The crucible temperature stability is estimated from the measured sensitivity of the evaporation rate of indium to temperature, and the observed variations in the evaporation rate for a fixed thermocouple temperature. The crucible temperature peak-to-peak variation over a one hour period is 1.2 °C. Machined molybdenum crucibles were used in the indium and copper sources for depositing CuInSe2 thin films for solar cells. © 2000 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
07.20.Ka High-temperature instrumentation; pyrometers
07.20.Hy Furnaces; heaters
07.07.Tw Servo and control equipment; robots

Production of metal oxide thin films by pulsed arc molecular beam deposition

Eric F. Rexer, Donald B. Wilbur, Jeffrey L. Mills, Robert L. DeLeon, and James F. Garvey

Rev. Sci. Instrum. 71, 2125 (2000); http://dx.doi.org/10.1063/1.1150593 (6 pages) | Cited 1 time

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Deposition for the first time of titanium oxide, cerium oxide, and tin oxide thin films by reactive pulsed arc molecular beam deposition is reported. To produce these thin films, oxygen gas was pulsed between a pair of electrodes situated within a vacuum chamber. A 20 μf storage capacitor was discharged between the electrode pair during the gas pulse. A substrate was placed inline with the oxygen pulse, on which an oxide coating of the electrode material was then coated. The films were analyzed by both scanning electron microscopy and electron spectroscopy for chemical analysis. There was a noted strong dependence of the film surface quality on the melting temperature of the starting electrode material. © 2000 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

A novel thermal desorption spectroscopy apparatus

Facundo J. Castro and Gabriel Meyer

Rev. Sci. Instrum. 71, 2131 (2000); http://dx.doi.org/10.1063/1.1150594 (3 pages) | Cited 2 times

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We present a new experimental setup designed to perform measurements of thermal desorption spectroscopy of hydrogen released from metallic samples. The distinctive features of the proposed arrangement are a compact reactor and the use of a mass flow meter to measure the flux of gas desorbed from the sample. A complete set of hydrogen desorption spectra from Pd samples has been recorded to test the equipment. The spectra show very good reproducibility, a high signal-to-noise ratio, and agree very well with results reported in the literature obtained using more sophisticated equipment. These features encourage the use of this low cost setup to perform a fast and reliable characterization of the processes controling hydrogen desorption from metallic compounds. © 2000 American Institute of Physics.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
07.30.Bx Degasification, residual gas
07.75.+h Mass spectrometers

Infrared optical switch by the use of optically excited free carriers in semiconductors

Mitsunori Saito and Takeshi Inoue

Rev. Sci. Instrum. 71, 2134 (2000); http://dx.doi.org/10.1063/1.1150595 (2 pages) | Cited 4 times

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Infrared light switching was achieved by using the infrared absorption due to the optically excited carriers in a semiconductor. A Nd:YAG laser pulse was used as a gate signal for excitation. A Si wafer was chosen as a switching element, since its band-gap energy coincides with the photon energy of the Nd:YAG laser. The intensity of incandescent infrared radiation was controlled by inducing free-carrier absorption in the Si wafer. © 2000 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Measurement of the absolute penetration depth and surface resistance of superconductors and normal metals with the variable spacing parallel plate resonator

Vladimir V. Talanov, Lucia V. Mercaldo, Steven M. Anlage, and John H. Claassen

Rev. Sci. Instrum. 71, 2136 (2000); http://dx.doi.org/10.1063/1.1150596 (11 pages) | Cited 10 times

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The variable spacing parallel plate resonator (VSPPR) is a microwave transmission line resonator with a continuously variable thickness of the dielectric spacer between the superconducting or metallic plates, filled by cryogenic liquid or vacuum. We measure the dielectric spacer thickness dependencies of the resonator frequency and quality factor, and fit them to theoretical forms, in order to extract the absolute values of penetration depth, λ, and surface resistance, Rs. A cryogenic micropositioning setup is developed to vary the spacer thickness from 0 to 100 μm with a resolution of 8.5 nm, and to maintain parallelism of the resonator plates. Measurement of ac capacitance between the plates is utilized to directly determine the separation between the resonator plates and to reduce the effect of their tilt and nonflatness on the accuracy of the measured Rs and λ. Because the operating temperature is fixed (77 K), the result for a superconductor is independent of an a priori model for the penetration depth versus temperature. This technique can also be employed as a surface impedance standard for characterization of high temperature superconducting films for microwave applications. © 2000 American Institute of Physics.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
74.25.Ha Magnetic properties including vortex structures and related phenomena
84.40.Az Waveguides, transmission lines, striplines
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
74.78.-w Superconducting films and low-dimensional structures
07.55.-w Magnetic instruments and components

Very high resolution measurement of the penetration depth of superconductors by a novel single-coil inductance technique

A. Gauzzi, J. Le Cochec, G. Lamura, B. J. Jönsson, V. A. Gasparov, F. R. Ladan, B. Plaçais, P. A. Probst, D. Pavuna, and J. Bok

Rev. Sci. Instrum. 71, 2147 (2000); http://dx.doi.org/10.1063/1.1150597 (7 pages) | Cited 18 times

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We describe a novel single-coil mutual inductance technique for measuring the magnetic penetration depth λ of superconductors at 2–4 MHz as a function of temperature in the 4–100 K range. We combine a single-coil configuration with a high-stability marginal oscillator; this enables us to measure the absolute value of λ on both bulk samples and thin films with very high resolution (δλ = 10 pm) and a precision of 30 nm. As example of application, we report measurements on NbTi bulk samples and Nb films. This contactless technique is suited for probing the superconducting properties of samples over large surfaces. © 2000 American Institute of Physics.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
07.55.-w Magnetic instruments and components

Thermal characterization of film-on-substrate systems with modulated thermoreflectance microscopy

Bincheng Li, L. Pottier, J. P. Roger, D. Fournier, and E. Welsch

Rev. Sci. Instrum. 71, 2154 (2000); http://dx.doi.org/10.1063/1.1150598 (7 pages) | Cited 12 times

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Computer simulations are performed in this article to show the feasibility of simultaneous determination of the film diffusivity, the substrate diffusivity, and the thermal boundary resistance of film-on-substrate systems by modulated thermoreflectance microscopy and multiparameter fitting. The dependences of the phase on the probe-to-pump beam separation, measured at four different modulation frequencies, are simultaneously fitted to an appropriate thermal diffusion model to extract the three thermal parameters. The selection of the optimal frequency combination is analyzed. Three samples: an 80 nm gold film on LaAlO3 and diamond substrates, and a 300 nm YBaCuO film on LaAlO3 substrate, are simulated. Experimental results are also presented to discuss the influence of the shape and irregularity of the beam on the fitting. The simulation results show that the statistical mean values of the three thermal parameters are very close to the input values, and the statistical errors of the film diffusivity and substrate diffusivity are comparable to the overall experimental error. However, the error of the thermal boundary resistance depends largely on the absolute thermal resistance value and the diffusivity difference between the film and the substrate. Under typical experiment conditions, the measurement errors of the two diffusivities are ∼ 5%, and error of the thermal boundary resistance is 10%–20%. © 2000 American Institute of Physics.
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78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
07.20.-n Thermal instruments and apparatus
68.60.Dv Thermal stability; thermal effects
78.66.-w Optical properties of specific thin films
07.60.Pb Conventional optical microscopes

Spectral analysis: A new method to measure the spontaneous polarization of ferroelectric liquid crystals

O. Gimenes Martins and A. M. Figueiredo Neto

Rev. Sci. Instrum. 71, 2161 (2000); http://dx.doi.org/10.1063/1.1150599 (5 pages) | Cited 1 time

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A new method to measure the spontaneous polarization density PS of ferroelectric liquid crystals as a function of the temperature is described. It is based on the spectral decomposition of the polarization and measurement of the different temporal harmonics using a lock-in amplifier. It is particularly adapted to measure small values of PS in regions where different nonlinear process compete. This condition is fulfilled at temperatures around the SmC∗–SmA transition temperature in liquid crystals. The method has a quantitative procedure to evaluate the saturation state of the sample’s polarization at a given applied electric field. It overcomes the difficulty of the subjective evaluation of the hysteresis loop present in the usual methods. The accuracy in the measurement of PS of the ZLI-3654 ferroelectric liquid crystal in the region of about 0.5 nC/cm2 is approximately one order of magnitude larger than that obtained with conventional hysteresis loop methods. © 2000 American Institute of Physics.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
77.22.Ej Polarization and depolarization
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.80.-e Ferroelectricity and antiferroelectricity
64.70.M- Transitions in liquid crystals
back to top CHEMISTRY

Diameter control of an extremely thin cylindrical microprobe by electrochemical etching

Y. M. Lim and S. H. Kim

Rev. Sci. Instrum. 71, 2166 (2000); http://dx.doi.org/10.1063/1.1150600 (3 pages) | Cited 1 time

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Electrochemical etching is shown to produce slender cylindrical tungsten probes used as microelectrodes for micromachining or in electrochemical studies. A mathematical model is derived for diameter control of the microprobes and its validation is investigated through experiments. © 2000 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
06.60.Vz Workshop procedures (welding, machining, lubrication, bearings, etc.)
81.65.Cf Surface cleaning, etching, patterning
82.47.-a Applied electrochemistry

Pulsed technique for observing infrared emissions from ionic gas phase reactions at low reactant ion concentrations

T. L. Williams, B. K. Decker, L. M. Babcock, N. G. Adams, and P. W. Harland

Rev. Sci. Instrum. 71, 2169 (2000); http://dx.doi.org/10.1063/1.1150601 (11 pages) | Cited 2 times

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A technique has been developed to detect infrared emissions from the products of ionic reactions in plasmas. The technique employs dual-phase digital lock-in amplification and cold filtering to permit the detection of the weak infrared chemiluminescence (IRCL) with a solid-state detector. A novel method of cleanly modulating plasma chemiluminescence by the pulsed introduction of reagent gases has been developed and implemented. This new technique has been tested by studying the well-characterized H-atom reactions, H+Cl2→HCl(v = 0–4)+Cl and H+NO2→OH(v = 0–3)+NO. Rotational and vibrational distributions have been measured for these two reactions and are presented and compared with previous determinations. Additionally, the associative electron detachment reaction, H+Cl−→HCl(v = 0–2)+e, has been studied, demonstrating that IRCL can be collected from reactions occurring at a low number density approaching that of the plasma ionization ( ∼ 4×1010 cm−3). The resolution, and hence, the information content of the collected emissions from this reaction have been greatly improved over previous work, with which our data are compared. © 2000 American Institute of Physics.
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82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
78.60.Ps Chemiluminescence
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
82.20.Hf Product distribution
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
back to top BIOLOGY and MEDICINE

Fast mixing device inside a nuclear magnetic resonance magnet: A tool for observing early steps in protein folding

M. Hamang, A. Sanson, L. Liagre, V. Forge, and P. Berthault

Rev. Sci. Instrum. 71, 2180 (2000); http://dx.doi.org/10.1063/1.1150602 (4 pages) | Cited 2 times

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We describe a device designed to perform a fast mixing of two solutions inside the magnet of a nuclear magnetic resonance (NMR) spectrometer. The apparatus is totally nonmagnetic; it operates via a system of pneumatic valves, which drives a syringe to inject the first solution into the NMR tube that already contains the other solution. An important point is that before and after the injection, the solution in the NMR tube is free of any perturbing injecting device. The injection is controlled by the spectrometer software in the NMR pulse sequence. Simple experiments have been performed to assess the viability of the device, and evaluate the dead time after injection, as well as the loss of homogeneity and the mixing capabilities. The device described can mix up to 200 μl of solution with the solution already present in the NMR tube in less than 50 ms, with a negligible loss of homogeneity during injection. The device was specifically designed for protein folding studies but can find a general purpose for chemical reactions involving small amounts of compounds. © 2000 American Institute of Physics.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
87.64.K- Spectroscopy
87.14.E- Proteins
87.15.Cc Folding: thermodynamics, statistical mechanics, models, and pathways
87.15.N- Properties of solutions of macromolecules

Cancellation technique of external noise inside a magnetically shielded room used for biomagnetic measurements

Akihiko Kandori, Tsuyoshi Miyashita, and Keiji Tsukada

Rev. Sci. Instrum. 71, 2184 (2000); http://dx.doi.org/10.1063/1.1150603 (7 pages) | Cited 7 times

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First-order gradiometers inside a magnetically shielded room (MSR) were used to cancel magnetic-field noise. However, the magnetic field inside a MSR is distorted when the amount of external noise is large. This distortion is caused by the low-pass filter property of the MSR. Therefore, the time constants of the frequency-dependent attenuation of the MSR vary spatially and this variation must be taken into account. To investigate noise cancellation, we used a multichannel superconducting quantum interference device consisting of four gradiometers measuring a source signal and two gradiometers as a reference. To compensate for the different magnitudes of the gradiometer wave forms, which differed because of slight differences in their pickup-coil cancel rates, we calculated a fitting parameter. The noise-cancellation method consisted of two processes: reduction of ambient noise caused by the differences in the cancel rate of the gradiometers and a gradient magnetic field inside the MSR, and cancellation of wave-form distortion caused by the spatial variation of the time constants inside the MSR. This cancellation method provides additional attenuation of over 20–30 dB in addition to the balance (>46 dB) of a first-order gradiometer. However, the remaining noise, especially a spike (<2 pT) at the beginning of a large ambient noise step, could not be completely canceled. This noise was caused by the slight difference between the time constants at the reference sensor position and at the signal sensor position. Except for this noise spike, however, the noise cancellation enabled clear magnetocardiogram wave forms to be measured without being affected by strong external noise. © 2000 American Institute of Physics.
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07.55.Nk Magnetic shielding in instruments
87.19.Hh Cardiac dynamics
87.50.C- Static and low-frequency electric and magnetic fields effects

Phase-amplitude crosstalk in intensity modulated near infrared spectroscopy

K. Alford and Y. Wickramasinghe

Rev. Sci. Instrum. 71, 2191 (2000); http://dx.doi.org/10.1063/1.1150604 (5 pages) | Cited 3 times

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Near infrared spectroscopy (NIRS) instruments that rely on phase sensitive detection suffer from what is called “phase-amplitude crosstalk,” i.e., the phase measured is dependent on the average light intensity entering the detector. Changes in detector rise time with input light intensity is the accepted explanation of this phenomenon. It is concluded here that an additional simple mechanism can cause phase-amplitude errors, particularly if the ratio of the ac component of the detected signal to the dc component is low. It is shown that the form of the phase distortion encountered during the development of a new phase sensitive NIR instrument can be modeled by assuming the presence of a synchronous interfering signal, due to rf coupling, at the detector output. This modeling allows a required margin between the detected signal of interest, i.e., the signal from the tissue and the interfering signal to be set in order to achieve a measured phase accuracy necessary to derive sufficiently accurate clinical parameters. © 2000 American Institute of Physics.
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87.64.K- Spectroscopy
42.62.Fi Laser spectroscopy
42.62.Be Biological and medical applications
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

Design of a scanning laser optical trap for multiparticle manipulation

C. Mio, T. Gong, A. Terray, and D. W. M. Marr

Rev. Sci. Instrum. 71, 2196 (2000); http://dx.doi.org/10.1063/1.1150605 (5 pages) | Cited 44 times

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In recent years, single-beam optical traps have been used to manipulate individual colloids and biological objects such as cells. We have implemented a rapidly scanning laser optical trap with rates as high as 1200 Hz where a single laser beam is used to trap multiple colloids simultaneously. The optics are optimized to achieve a small laser focus size and a large scanning pattern in the sample. This approach provides great pattern flexibility and, because of the use of piezoelectrics, small particles (1 μm in diameter) in low-viscosity solvents, such as water, can be readily manipulated. © 2000 American Institute of Physics.
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37.10.Vz Mechanical effects of light on atoms, molecules, and ions
87.80.Cc Optical trapping
82.70.Dd Colloids
06.60.Sx Positioning and alignment; manipulating, remote handling
07.60.Pb Conventional optical microscopes
42.62.Be Biological and medical applications

Fluorescence measurements on nanotiter plates

M. Hessling, J. Ihlemann, and G. Marowsky

Rev. Sci. Instrum. 71, 2201 (2000); http://dx.doi.org/10.1063/1.1150606 (5 pages) | Cited 2 times

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Two different highly sensitive and fast but low-cost instruments for fluorescence measurements on nanotiter plates or other high density sample arrays are presented. Both instruments use 635 nm diode lasers for the detection of Cy5 fluorescence. In the first device all cavities of the nanotiter plate are illuminated simultaneously and the fluorescence is detected spatially resolved by a charge-coupled device camera within a few seconds. The second system uses an on-chip microscanner for the sequential illumination of the samples and the fluorescence is detected by a simple photomultiplier tube. Both instruments have originally been developed for environmental analysis by immunochemical labeling but they can also be used for other medical and biological purposes where analyte concentrations have to be determined. © 2000 American Institute of Physics.
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87.64.K- Spectroscopy
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.79.Pw Imaging detectors and sensors
back to top GRAVITY; GEOPHYSICS; ASTRONOMY and ASTROPHYSICS

Full scale prototype of high Q pendulum for interferometric gravitational wave detectors

G. Cagnoli, L. Gammaitoni, J. Kovalik, F. Marchesoni, and M. Punturo

Rev. Sci. Instrum. 71, 2206 (2000); http://dx.doi.org/10.1063/1.1150607 (5 pages) | Cited 8 times

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A series of measurements were undertaken to measure the quality factor of a full scale prototype of the last stage suspension system (a 21 kg pendulum) of the VIRGO gravitational wave interferometer, by using a structure with negligible recoil losses. The suspension wires consisted of two loops of C85 harmonic steel with a diameter of 200 μm that formed a pendulum with a length of 0.70 m. The measured pendulum Q varied from ∼ 1×104 for the wire simply cradling the mass to 8×105 for the wire being offset from the mass with a prism shaped spacer, while the theoretical value for the pendulum Q was calculated to be 6.7×106. The best measured Q was 1.1×106 for a 20 kg glass mass with metal clamps rigidly attached to it. The main factor that limits the pendulum Q is the dissipation in the wire–test mass attachment. More advanced designs using new materials are needed in order to increase the pendulum Q significantly. © 2000 American Institute of Physics.
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04.80.Nn Gravitational wave detectors and experiments
95.55.Ym Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques
07.60.Ly Interferometers
07.10.-h Mechanical instruments and equipment
back to top GENERAL INSTRUMENTS

A two-axis micromachined silicon actuator with micrometer range electrostatic actuation and picometer sensitive capacitive detection

F. Ayela, J. L. Bret, J. Chaussy, T. Fournier, and E. Ménégaz

Rev. Sci. Instrum. 71, 2211 (2000); http://dx.doi.org/10.1063/1.1150608 (8 pages) | Cited 6 times

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This article presents an innovative micromachined silicon actuator. A 50-μm-thick silicon foil is anodically bonded onto a broached Pyrex substrate. A free standing membrane and four coplanar electrodes in close proximity are then lithographied and etched. The use of phosphorus doped silicon with low electrical resistivity allows the application of an electrostatic force between one electrode and the moving diaphragm. This plane displacement and the induced interelectrode variation are capacitively detected. Due to the very low electrical resistivity of the doped silicon, there is no need to metallize the vertical trenches of the device. No piezoelectric transducer takes place so that the mechanical device is free from any hysteretic or temperature dependance. The range of the possible actuation along the x and y axis is around 5 μm. The actual sensitivity is xn = 0.54 Å/Hz1/2 and yn = 0.14 Å/Hz1/2. The microengineering steps and the electronic setup devoted to design the actuator and to perform relative capacitive measurements ΔC/C = 10−6 from an initial value C ≈ 10−13 F are described. The elaborated tests and performances of the device are presented. As a conclusion, some experimental projects using this subnanometric sensitive device are mentioned. © 2000 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
81.20.Wk Machining, milling
81.65.Cf Surface cleaning, etching, patterning
07.07.Tw Servo and control equipment; robots

Capacitance based scanner for thickness mapping of thin dielectric films

John Graham, Marek Kryzeminski, and Zoran Popovic

Rev. Sci. Instrum. 71, 2219 (2000); http://dx.doi.org/10.1063/1.1150609 (5 pages) | Cited 4 times

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We have recently developed a technique capable of mapping variations in the thickness of thin dielectric films. This technique is based on accurately recording the capacitance between a spherical probe and the conductive substrate of a dielectric film. Once the capacitance has been recorded, and assuming the dielectric constant is known, the thickness of the film can be readily extracted, with better than 0.2 μm accuracy. In the current experimental configuration, the probe can be raster scanned with respect to the surface of the dielectric film, enabling one to record three-dimensional images and observe any spatial variations in sample thickness. The spatial resolution (i.e., the imaging resolution) of the technique is primarily dictated by the size of the probe and currently rests at ∼200 μm. This technique is applicable to any dielectric film on a conductive substrate, assuming the dielectric constant is known. © 2000 American Institute of Physics.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.68.+m Photography, photographic instruments; xerography
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
77.55.-g Dielectric thin films
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