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Apr 1996

Volume 67, Issue 4, pp. 1425-1689

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Fluorescence microscopy in superfluid helium: Single molecule imaging

Jan Jasny, Jerzy Sepiol, Thomas Irngartinger, Markus Traber, Alois Renn, and Urs P. Wild

Rev. Sci. Instrum. 67, 1425 (1996); http://dx.doi.org/10.1063/1.1146868 (6 pages) | Cited 34 times

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A fluorescence microscope for the detection of spatially resolved single molecules at low temperature has been developed. The main part consists of a microscope objective which is inserted in superfluid helium. Two versions of the optical system are described. Both setups have a high numerical aperture and thus high collection efficiency. A video camera with an image intensifier is used to detect the fluorescence images. Detection of single molecule fluorescence has been achieved. It was even possible to visualize individual fluorescing molecules on a video monitor in real time. Spectroscopic applications of this parallel detection scheme are discussed. © 1996 American Institute of Physics.
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07.60.-j Optical instruments and equipment
33.50.-j Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion)
07.77.-n Atomic, molecular, and charged-particle sources and detectors

Isotope separation in a magneto‐optical trap

H. R. Noh, J. O. Kim, D. S. Nam, and W. Jhe

Rev. Sci. Instrum. 67, 1431 (1996); http://dx.doi.org/10.1063/1.1146869 (3 pages) | Cited 3 times

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We demonstrate simultaneous trapping and spatial separation of the two stable rubidium isotopes in a magneto‐optical trap. To realize this novel type of isotope separation, we have built a compact diode laser which is frequency‐stabilized by optical feedback from a diffraction grating, and frequency‐modulated by a direct microwave modulation of the bias current from a yittrium iron garnet tuned oscillator. Use of the single diode laser with microwave sidebands provides much ease and flexibility in the applications of a magneto‐optical trap. © 1996 American Institute of Physics.
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28.60.+s Isotope separation and enrichment
37.10.De Atom cooling methods
37.10.Gh Atom traps and guides
42.62.-b Laser applications

Fiber optic velocity interferometer with very short coherence length light source

L. Levin, D. Tzach, and J. Shamir

Rev. Sci. Instrum. 67, 1434 (1996); http://dx.doi.org/10.1063/1.1146895 (4 pages) | Cited 10 times

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A novel fiber optic velocity interferometer for velocity measurements of moving surfaces has been developed and tested. The interferometer is based on optical fibers or fiber coupled components only and therefore is compact, portable, easy to align, and enables measurements in hard to reach locations. It also does not require a source of long coherence length (only a few wavelengths, regardless of the optical path difference or the surface displacement). This interferometer removes the directional ambiguity of the acceleration using a [3×3] optical coupler. © 1996 American Institute of Physics.
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07.60.Vg Fiber-optic instruments
07.60.Ly Interferometers
06.30.Gv Velocity, acceleration, and rotation

Spectral measurements of hyper‐Rayleigh light scattering

P. Kaatz and D. P. Shelton

Rev. Sci. Instrum. 67, 1438 (1996); http://dx.doi.org/10.1063/1.1146870 (7 pages) | Cited 20 times

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An apparatus is described for the measurement of second‐order nonlinear optical properties via hyper‐Rayleigh scattering with 1 cm−1 spectral resolution of the scattered light. The setup allows a complete investigation of the polarization dependence of the second‐harmonic scattered light. The combination of good spectral resolution, polarization analysis, and high sensitivity allows the determination of accurate polarization ratios of the scattered light. Consequently, information on the relative magnitude of hyperpolarizability components may be inferred from the measurements. Liquid phase measurements of a number of pure organic solvents including substituted benzene compounds are reported with approximately 5% uncertainty in the relative scattered intensities. Vapor phase measurements are also possible using the same apparatus, allowing a separation of the intrinsic molecular nonlinearities from contributions to hyper‐Rayleigh scattering due to intermolecular interactions. © 1996 American Institute of Physics.
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07.60.Rd Visible and ultraviolet spectrometers
42.65.-k Nonlinear optics

Measurement of first hyperpolarizabilities by hyper‐Rayleigh scattering

I. D. Morrison, R. G. Denning, W. M. Laidlaw, and M. A. Stammers

Rev. Sci. Instrum. 67, 1445 (1996); http://dx.doi.org/10.1063/1.1146871 (9 pages) | Cited 53 times

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The origin of spurious and irreproducible signals in the measurement of the hyper‐Rayleigh scattering (HRS) of solutions is investigated. A new cell design, coupled with continuous solution filtration through a 20 nm filter, is shown to improve the reproducibility of the measurement to ±5%. A transverse cell dimension of ∼2 mm reduces absorption of the second harmonic. A simple monochromaticity test is used to identify luminescence, and we recommend that it is made routinely. Scattering from the [Ru(bipy)3]2+ cation, attributed to HRS by Zyss et al. [Chem. Phys. Lett. 206, 409 (1993)], appears to be largely due to two‐photon excited luminescence. The reliability of calibration procedures is examined, and some revised hyperpolarizabilities are reported. © 1996 American Institute of Physics.
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42.65.-k Nonlinear optics
07.60.Rd Visible and ultraviolet spectrometers

A simple method to fabricate lenses for in situ Fourier transform infrared spectroscopy

Lia M. Treffman and Philip W. Morrison

Rev. Sci. Instrum. 67, 1454 (1996); http://dx.doi.org/10.1063/1.1146872 (4 pages) | Cited 1 time

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A process has been developed to hand grind and polish infrared KBr lenses with a wide choice of focal lengths. These lenses are designed for coupling the infrared (IR) beam from a Fourier transform infrared spectrometer into a hot filament chemical vapor deposition reactor. These IR lenses are ground using a glass lens as a mold; the mold lens is a commercial glass lens used for spectacles and is available in a wide range of focal lengths. Rough grinding begins with ♯100 sandpaper and followed by a sequence of fine grinding steps under ethanol: ♯400 SiC powder, ♯600 SiC powder, and emery powder. Polishing is done with a CeO slurry in water followed by a chamois cloth moistened with ethanol. As an indication of the surface finish of the lenses, a flat KBr window that is hand ground and polished in the above manner has a transmission of ≳89% at 8000 cm−1 and ≳91% at 500 cm−1; the commercially polished KBr window has a transmittance of 92% throughout this spectral range. © 1996 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.86.+b Optical workshop techniques
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Examining deep holes by rocking the beam in the scanning electron microscope

Oliver C. Wells

Rev. Sci. Instrum. 67, 1458 (1996); http://dx.doi.org/10.1063/1.1146873 (5 pages) | Cited 1 time

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The beam‐rocking method in the scanning electron microscope can show either the inner surface of a deep hole or the outer surface of a parallel‐sided pillar in ways that are not possible when scanning in the usual way. This has been demonstrated using test samples of both kinds. It is believed that this method can be successfully applied to examine deep holes and narrow pillars of micrometer dimensions by applying computer control and data analysis techniques of the kind that are used in automated semiconductor fabrication and/or metrology systems. © 1996 American Institute of Physics.
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68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
41.85.Gy Chromatic and geometrical aberrations
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Vacuum compatible high‐sensitive Kelvin probe force microscopy

Atsushi Kikukawa, Sumio Hosaka, and Ryo Imura

Rev. Sci. Instrum. 67, 1463 (1996); http://dx.doi.org/10.1063/1.1146874 (5 pages) | Cited 45 times

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A vacuum compatible Kelvin probe force microscopy (KPFM) is presented. Difficulties in operating KPFM in a vacuum were overcome by utilizing the direct cantilever resonance frequency detection in the tip height control whereas the indirect resonance frequency detection scheme was used in primordial KPFM. The potential measurement sensitivity was improved by 14 dB compared to that in air. It is due to the increased cantilever Q value and the reduction in the interference from the tip height detection signal because potential measurement is conducted using the cantilever’s second resonance while tip height control was conducted using the first resonance. A silicon wafer whose surface is partially doped with arsenic by ion implantation was observed, and surface potential difference at the junctions were clearly imaged. © 1996 American Institute of Physics.
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07.50.-e Electrical and electronic instruments and components
73.30.+y Surface double layers, Schottky barriers, and work functions

An impedance based non‐contact feedback control system for scanning probe microscopes

Mark Lee, E. B. McDaniel, and J. W. P. Hsu

Rev. Sci. Instrum. 67, 1468 (1996); http://dx.doi.org/10.1063/1.1146875 (4 pages) | Cited 34 times

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We describe a non‐contact, non‐optical distance feedback control system for scanning probe microscopes that detects the surface damping of a vibrating probe. The feedback signal is derived from an electrical impedance change in a dithering piezoelectric element with attached scanning tip. The system incorporates an arbitrary‐impedance bridge that maximizes detection sensitivity of the surface damping‐induced impedance change as the tip approaches and interacts with the sample. In addition, an auxiliary circuit greatly improves reliability by making the feedback signal insensitive to the phase of the impedance change. The complete detection network can sense changes of −80 to −100 dB down to the level of 1 μV in a bandwidth of ≳1 kHz. The feedback system has demonstrated topographic height sensitivity of ∼0.5 Å and dynamic range of ≳60 dB. © 1996 American Institute of Physics.
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07.05.Dz Control systems
07.79.-v Scanning probe microscopes and components

A three‐axis micropositioner for ultrahigh vacuum use based on the inertial slider principle

R. Erlandsson and L. Olsson

Rev. Sci. Instrum. 67, 1472 (1996); http://dx.doi.org/10.1063/1.1146876 (3 pages) | Cited 8 times

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We present a three‐dimensional micropositioner using the inertial slider principle which is used to position an optical fiber in an atomic force microscope. It uses only two moving parts as the sideways and vertical motions are realized by either moving a cylinder along its axis or rotating it around its axis and translating the rotation into an approximately vertical motion. The device operates reliably in a baked ultrahigh vacuum system, allows positioning with sub‐μm accuracy, and has a forward range of 11.3 mm, a sideways range of 5 mm, and a vertical range of approximately 5 mm. The measured speeds without extra load fall in the range between 1.6 and 3.3 mm/min, in good agreement with the amplitude and curve shape of the applied drive signal. The minimal step size allowing consistent motion is below 25 nm. © 1996 American Institute of Physics.
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06.60.Sx Positioning and alignment; manipulating, remote handling
07.79.Lh Atomic force microscopes

Three‐dimensional analyses for motions of trapped microparticles in the TRISTAN accumulation ring

Hiroshi Saeki, Takashi Momose, and Hajime Ishimaru

Rev. Sci. Instrum. 67, 1475 (1996); http://dx.doi.org/10.1063/1.1146877 (3 pages) | Cited 3 times

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Signals of high‐energy bremsstrahlung different from previous results of periodic pair signals were observed using a gamma‐ray detector during microparticle trapping in the TRISTAN accumulation ring. Therefore, more precise three‐dimensional analyses for motions of trapped microparticles around the electron beam were carried out. The analyses nearly coincided with the results of observation. © 1996 American Institute of Physics.
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41.60.-m Radiation by moving charges
29.20.db Storage rings and colliders

Generation of a fast atomic‐oxygen beam from O− ions by resonant cavity radiation

T. M. Stephen, B. Van Zyl, and R. C. Amme

Rev. Sci. Instrum. 67, 1478 (1996); http://dx.doi.org/10.1063/1.1146878 (5 pages) | Cited 3 times

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An apparatus has been developed for producing a beam of ground‐electronic‐state oxygen atoms with energies variable from 4 to 1000 eV with a 1.5 eV FWHM energy distribution. The technique involves extraction of negative ions from a low‐voltage gas‐discharge source, mass selection of the extracted O− with a Wien‐type velocity filter, O− acceleration or deceleration and focusing by electrostatic ion optics, and electron detachment from O− by intracavity laser radiation. A 25 W argon‐ion‐laser cavity has been extended to include the ion‐beam vacuum chamber so that the intracavity radiation intersects the O− ion trajectories normally. Depending on the laser configuration in use, ion‐neutralization efficiencies between 5% and 25% have been achieved at 5 eV O− energy. Thus, 5 eV O‐atom fluxes of ∼1011 atoms/s (∼1012 atoms/cm2 s) have been achieved for O− currents of ∼10−7 A. The advantages and limitations of the technique are discussed, and preliminary measurements of the secondary‐negative‐charge production from low‐energy O‐atom impact on copper and stainless‐steel surfaces are presented. © 1996 American Institute of Physics.
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07.77.Gx Atomic and molecular beam sources and detectors
37.20.+j Atomic and molecular beam sources and techniques
34.35.+a Interactions of atoms and molecules with surfaces

A simple model to describe ion source extraction optics—Simulations and experimental test

S. Biri, A. Báder, and J. Pálinkás

Rev. Sci. Instrum. 67, 1483 (1996); http://dx.doi.org/10.1063/1.1146879 (3 pages) | Cited 1 time

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The main goal of this work was to experimentally check the value of the ‘‘cos+lin’’ method previously developed by the authors. The design and optimization of the beam extraction optics for a hollow‐cathode ion source have been carried out. Starting from an existing electrode arrangement the optical system (e.g., the shape and potential of the electrodes) was gradually fitted to the requirements of the model. The final optimization of the optics was carried out by the SIMION computer code. We tested the extraction and focusing optics with H+ and Ar+ ions at different energies up to 30 keV. The electrode potentials, optimized for the best beam parameters (the largest intensity and smallest diameter), are in good agreement with the calculated values. © 1996 American Institute of Physics.
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41.85.Ar Particle beam extraction, beam injection
07.77.Ka Charged-particle beam sources and detectors

Conceptual design of a beam extraction electrode system for a 1 mN ion thruster

G. M. Sandonato and J. J. Barroso

Rev. Sci. Instrum. 67, 1486 (1996); http://dx.doi.org/10.1063/1.1146880 (8 pages)

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Conceptual modeling of the multiaperture electrode system of a 5‐cm‐diam ring cusp ion thruster intended for producing a 1 mN thrust is described. A mathematical treatment of the ion extraction from the plasma has been developed to provide a method for calculating both the shape and potential of the plasma‐emitting surface. The ion optics of the electrode system have been examined using a numerical code to evaluate the ion beam divergence. Close agreement is achieved between the predictions of the conceptual modeling presented here and published experimental results. © 1996 American Institute of Physics.
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52.75.Di Ion and plasma propulsion
41.85.Ar Particle beam extraction, beam injection

Simulations of the response function of a plasma ion beam spectrometer for the Cassini mission to Saturn

J. H. Vilppola, P. J. Tanskanen, H. Huomo, and B. L. Barraclough

Rev. Sci. Instrum. 67, 1494 (1996); http://dx.doi.org/10.1063/1.1146881 (8 pages) | Cited 3 times

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To obtain very high (∼1%) energy resolution with spherical‐section electrostatic analyzers requires high precision in both fabrication and in the alignment process. In order to aid in the calibration of the instrument and to help minimize fabrication costs, we have applied simulation models to the ion beam spectrometer for the NASA/ESA Cassini mission to Saturn. In our previous article we studied the effects of misalignment and simple irregularities of the hemispherical surfaces on the performance of an electrostatic analyzer. We have considered a hemispherical electrostatic analyzer equipped with an aperture plate to collimate the stray electric field at the entrance apertures. The influence of a curved entrance aperture has also been added to the simulation model, and its effects have been studied in detail. A cylindrical three‐dimensional simultaneous overrelaxation algorithm has been introduced to solve for the stray electric field. The maximum loss of transmitted particles with respect to the transmission of an ideal instrument has been set at 10%. We demonstrate that the deviation in the distributions of the energies is less than 0.2% and that the deviation in the distributions of entrance angles of transmitted particles is less than 0.1°. It has been found that the energy resolution of an electrostatic analyzer can be improved from ΔE/E=(1.6±0.2)% to ΔE/E=(1.3±0.2)% by the introduction of front aperture plates. Through the introduction of curved entrance slits, the azimuthal angle resolution has changed from β=(1.4±0.1)° for the simplified geometry simulation results of our previous article to β=(2.3±0.1)°. We have confirmed that an accuracy of 25 μm in the alignment of the two hemispherical surfaces is sufficient to give the instrument the desired resolutions. © 1996 American Institute of Physics.
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07.81.+a Electron and ion spectrometers
07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)
41.85.Qg Particle beam analyzers, beam monitors, and Faraday cups

Control of plasma parameters in sheet‐shaped electron cyclotron resonance heating plasma supplemented with radio frequency discharge

Kanetoshi Shibata, Noboru Yugami, Yasushi Nishida, and Tadaomi Miyazaki

Rev. Sci. Instrum. 67, 1502 (1996); http://dx.doi.org/10.1063/1.1146894 (6 pages) | Cited 2 times

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Production and parameter control techniques of sheet‐shaped electron cyclotron resonance heating (ECRH) plasma are described. When rf power (f≂13.56 MHz) is supplemented by the sheet‐shaped ECR plasma, the ion temperature, Ti, ion fluxes, nb/n0, and high energy component, ϵi, of ions deposited to the substrate can be controlled arbitrarily within the range of 0.3 eV≤Ti≤10.0 eV, 0≤nb/n0≤30%, and 0≤ϵi≤60 eV, respectively, in the neutral Ar gas pressure, 4×10−4≤p≤3×10−3 Torr. Furthermore, the ion energy and/or the ion flux flowing onto the substrate could be well controlled by changing the bias voltage supplied to the substrate holder. We can expect that the present experimental technique could be applied to the material processing in a well‐defined manner. © 1996 American Institute of Physics.
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52.50.Gj Plasma heating by particle beams
52.80.Pi High-frequency and RF discharges
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

High sensitivity, inductively coupled miniature magnetic probe array for detailed measurement of time varying magnetic field profiles in plasma flows

D. C. Black and R. M. Mayo

Rev. Sci. Instrum. 67, 1508 (1996); http://dx.doi.org/10.1063/1.1146882 (9 pages) | Cited 6 times

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A modified math circuit design has been implemented as part of a miniature magnetic probe array for the Coaxial Plasma Source experiment [R. M. Mayo et al., Plasma Sources Sci. Technol. 4, 47 (1995)] at the North Carolina State University. This facility is currently being used for the generation of energetic plasma flows to allow laboratory study of magnetogasdynamics with particular emphasis on the importance of the Hall effect [D. C. Black et al., Phys. Plasma 1, 3115 (1994)] and plasma microinstabilities [R. M. Mayo et al., Phys. Plasma 2, 337 (1995)] to plasma transport in coaxial plasma sources. The miniature magnetic probe array consists of ten spatially separated coils wound on an Acetal form of dimensions 2.38 cm by 0.32 cm by 0.32 cm. At five positions, with roughly 0.32 cm separation, two mutually perpendicular coils are wound to measure the magnetic field in the θ and math directions. The modification to the signal processing circuitry consists of the use of a step‐up transformer to boost the probe signal prior to filtering and acquiring the signal at the data acquisition system. This additional means of amplifying the signal allows for reduction in the size of the probe, and thus helps minimize the perturbing effect of the magnetic probe on the plasma. An additional advantage of using a signal transformer is that it provides electrical isolation between the experiment and the data acquisition system. © 1996 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements

Multiple hollow‐cathode vacuum‐ultraviolet plasma source excited by pulsed glow discharge

Setsuo Suzuki and Etsuo Noda

Rev. Sci. Instrum. 67, 1517 (1996); http://dx.doi.org/10.1063/1.1146883 (3 pages)

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A multiple hollow‐cathode vacuum‐ultraviolet source excited by a pulsed glow discharge in a mixture of Xe and He has been developed. A MgF2 window with a diameter of 55 mm was used, and the repetition frequency was varied between 3 and 9 kHz. Stable output was maintained for about 3 h. Measurements of 147 nm radiant illumination were made at various distances from the window at various repetition frequencies. The peak radiant illumination decreased while the average radiant illumination increased with increasing repetition frequency. The output power density near the center of the window could be estimated from the relationship between measured radiant illumination and distance from the window. The peak and average output power densities at 6 kHz were 30 and 1.5 W/m2, respectively. © 1996 American Institute of Physics.
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42.72.Bj Visible and ultraviolet sources
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Hc Glow; corona

Dual CO2 laser interferometer with a wavelength combination of 10.6 and 9.27 μm for electron density measurement on large tokamaks

Yasunori Kawano, Akira Nagashima, Takaki Hatae, and Soichi Gunji

Rev. Sci. Instrum. 67, 1520 (1996); http://dx.doi.org/10.1063/1.1146892 (9 pages) | Cited 17 times

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A new CO2 laser interferometer has been developed to measure the electron density of tokamak plasmas. Two different wavelength oscillators of 10.6 and 9.27 μm are utilized for simultaneous measurement of the density component and the optical path length change. A new technique using a common frequency shifter for two color lasers improves the stability of the system by a complete matching of both beat frequencies. The system provides advantages for practical problems of large tokmaks related to window darkening and large mechanical vibrations of reflection mirrors and offers improved laser beam monitoring and a simplified optical layout by using closer wavelengths. The electron density of JT‐60U is successfully measured for a plasma current of up to 3 MA. The density behavior during a fast major disruption is also diagnosed without a fringe loss. An effective density resolution is observed to be 2×1019 m−2, which corresponds to about 1/10 of a fringe. A very high resolution (1/104 fringe) phase comparator has been developed to improve the density resolution of the dual CO2 system. The performance achieved shows the feasibility of the dual CO2 laser interferometer for future large devices such as the International Thermonuclear Experimental Reactor. © 1996 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks

A small, insertable oven for boronization

D. A. Brouchous, D. A. Diebold, and M. L. Doczy

Rev. Sci. Instrum. 67, 1529 (1996); http://dx.doi.org/10.1063/1.1146896 (4 pages)

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A small insertable oven for benchmarking the boronizing characteristics of solid compounds, such as decaborane and carborane, has been developed for the Phaedrus‐T tokamak. Assembly and installation of the oven are relatively easy as the oven design utilizes a Langmuir probe drive assembly, which is standard equipment on most tokamaks and allows the oven to be inserted into the tokamak without requiring a vent. Films deposited by heating carborane into the vapor state with the oven are found to be spatially nonuniform in both thickness and in the ratio of boron to carbon as compared to films deposited with trimethylboron, a gaseous compound. Overall plasma performance is not found to be greatly affected by whether decaborane, carborane or trimethylboron is used for boronization in Phaedrus‐T. © 1996 American Institute of Physics. <ii;010512>
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28.52.Lf Components and instrumentation
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

A high impedance mega‐ampere generator for fiber z‐pinch experiments

I. H. Mitchell, J. M. Bayley, J. P. Chittenden, J. F. Worley, A. E. Dangor, M. G. Haines, and P. Choi

Rev. Sci. Instrum. 67, 1533 (1996); http://dx.doi.org/10.1063/1.1146884 (9 pages) | Cited 81 times

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At Imperial College a mega‐ampere generator for plasma implosion experiments has been designed, built, and commissioned. With a final line impedance of 1.25 Ω this terawatt class generator has been designed primarily to drive a maximum current of 1.8 MA with a rise time of 150 ns into high inductance z‐pinch loads of interest to radiative collapse studies. This article describes the design and tests of the generator which has a novel configuration of lines and a new design of a magnetically insulated transmission line (MITL). In summary, the generator consists of four Marx generators each of the Hermes III type (2.4 MV, 84 kJ), each connected to 5 Ω pulse forming lines and trigatron gas switches. The power is fed into the matched 1.25 Ω vertical transfer line which feeds a diode stack and a short conical MITL in vacuum which concentrates the power into the z‐pinch load. At 80% charge a current rising to 1.4 MA in 150 ns has been measured in a 15 nH inductive short. Similar results are obtained when using a plasma load. © 1996 American Institute of Physics.
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84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
52.55.Ez Theta pinch

Inductively coupled radio frequency plasma chemical vapor deposition using a ladder‐shaped antenna

Masayoshi Murata, Yosiaki Takeuchi, Eishiro Sasagawa, and Kazutoshi Hamamoto

Rev. Sci. Instrum. 67, 1542 (1996); http://dx.doi.org/10.1063/1.1146885 (4 pages) | Cited 10 times

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Radio‐frequency (rf) excited SiH4 plasma is produced with an electrode of a ladder‐shaped antenna which is positioned within a plasma chamber. The negative self‐bias potential on the electrode is a few volts under a gas pressure 50 mTorr, rf power of 20–100 W. It was observed that the phase of the potential precedes the current fed to the electrode. Hydrogenated amorphous silicon films are formed on a 300 mm×300 mm substrate with a uniformity of ±15%. © 1996 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Gas temperature in a hot filament diamond chemical vapor deposition system

K. L. Menningen, M. A. Childs, L. W. Anderson, and J. E. Lawler

Rev. Sci. Instrum. 67, 1546 (1996); http://dx.doi.org/10.1063/1.1146886 (9 pages) | Cited 7 times

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The gas temperature in a hot filament activated diamond chemical vapor deposition system is derived from the vacuum ultraviolet absorption spectrum of the H2 molecule. Curves of growth for the optically thick spectra are calculated using a Voigt line shape and published oscillator strengths in order to measure relative populations of H2 in various rotational and vibrational levels of the ground electronic state. The H2 vibrational levels are nearly in equilibrium. The gas temperature field is most strongly influenced by the substrate temperature. Heat conduction from the filament produces a large temperature gradient near the filament. Heat released or absorbed in gas phase hydrocarbon chemical reactions does not significantly affect the temperature field. © 1996 American Institute of Physics.
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07.20.Ka High-temperature instrumentation; pyrometers
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.ub Fullerenes and related materials
33.20.Lg Ultraviolet spectra

Gallium arsenide as an optical strain gauge

Jonathan D. Weiss, Salvador S. Lopez, and Arnold J. Howard

Rev. Sci. Instrum. 67, 1555 (1996); http://dx.doi.org/10.1063/1.1146866 (9 pages)

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We have investigated the use of gallium arsenide (GaAs) as an optical strain gauge, presuming the shift in its absorption edge with uniaxial stress as the principle of operation. In our experiments, optical fibers guided light of the GaAs samples from a laser diode source and from the samples to an optical detector, as might be the case in a practical application of such a device. Compressive and tensile strains were developed in the samples by flexing a cantilevered beam to which they were bonded. An important understanding of this strain distribution was obtained with the help of a finite‐element calculation. The effects of sample width and the input optical energy distribution on the strain‐induced change in optical transmission were measured. In the case of the distribution with the shortest median wavelength, over 80% change in transmission was observed for a compressive strain of only 0.05%. In addition, we calculated the strain sensitivity of this device, assuming only a rigid, strain‐induced shift in its absorption edge. A comparison between experiment and calculation suggests that strain also caused the band edge of these samples to steepen in compression and broaden in tension. Another calculation suggests that this phenomenon is not intrinsic to the material. © 1996 American Institute of Physics.
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07.60.-j Optical instruments and equipment
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Two‐beam photoacoustic phase measurement of the thermal diffusivity of a Gd‐doped bulk YBCO superconductor

M. Aravind, P. C. W. Fung, S. Y. Tang, and H. L. Tam

Rev. Sci. Instrum. 67, 1564 (1996); http://dx.doi.org/10.1063/1.1146887 (6 pages) | Cited 3 times

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The two‐beam photoacoustic phase measurement was applied to measure quantitatively the thermal diffusivity (αs) of a ceramic bulk high‐Tc superconductor. Neglecting the effects of thermal dilation, and thermoelastic bending was proved valid in accordance with our composite piston model for the chosen experimental conditions. It was found that αs shows different features at the onset and offset temperatures corresponding to the normal–superconducting (NS) transition. A dip was seen at the resistivity transition onset temperature and a cusp at the offset temperature where the electrical resistance disappears. The presence of the cusp at the offset temperature is proposed to be related to weak coupling between superconducting grains. Our studies indicate that the two‐beam phase measurement is a very sensitive method for superconductor characterization and NS transition detection. The experimental results also confirm the presence of a large energy gap and strong electron–phonon coupling mechanism in the YBCO superconductor. © 1996 American Institute of Physics.
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07.20.-n Thermal instruments and apparatus
74.25.Bt Thermodynamic properties
74.72.-h Cuprate superconductors
07.64.+z Acoustic instruments and equipment
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