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Sep 1992

Volume 63, Issue 9, pp. 4041-4229

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A combined scanning electron microscope and scanning tunneling microscope for studying nanostructures

G. C. Rosolen and M. E. Welland

Rev. Sci. Instrum. 63, 4041 (1992); http://dx.doi.org/10.1063/1.1143262 (5 pages) | Cited 10 times

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An instrument which incorporates an electrostatic scanning electron microscope and a scanning tunneling microscope in an ultrahigh vacuum environment has been developed to study nanostructures. To facilitate positioning the nanostructures for examination with the instrument a high precision orthogonal motion sample stage has been designed. The instrument has been applied to locate and study both nanometer size trenches and wires. These structures have been fabricated using electron beam lithography and a polymethlymethacrylate lift‐off process.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Improved scanning tunneling microscope feedback for investigation of surfaces with micron‐scale roughness

D. Scholl, M. P. Everson, R. C. Jaklevic, and Weidian Shen

Rev. Sci. Instrum. 63, 4046 (1992); http://dx.doi.org/10.1063/1.1143263 (3 pages) | Cited 6 times

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When scanning steeply sloped features which are near micron size or taller, scanning tunneling microscopes with conventional feedback control loops exhibit slower response on downhill slopes than on uphill slopes. This effect is caused by the exponential dependence of the tunneling current on the tip‐sample distance. A gap smaller than the setpoint produces a sizable error signal, whereas a gap larger than the setpoint gives only a weak error signal. As the scan rate is increased, the tip begins ‘‘flying’’ well above the surface on steep downhill regions. We have developed a modification of the conventional integral feedback system which eliminates this problem. This circuit makes the error signal growth with increasing distance between the tip and sample similar to the usual exponential growth when the tip‐sample distance decreases. This modification allows an increase in scan rates by a factor of 5–10 with no reduction in image quality. The modification can be dialed in or out of circuit as needed, such as when switching between large scale images and atomic scale images, and can easily be installed in any existing scanning tunneling microscope that uses an analog feedback circuit.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

A variable temperature scanning tunneling microscope for use in ultrahigh vacuum

Robert A. Wolkow

Rev. Sci. Instrum. 63, 4049 (1992); http://dx.doi.org/10.1063/1.1143264 (4 pages) | Cited 16 times

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A design is presented for a scanning tunneling microscope (STM) capable of operation over a temperature range of approximately 80–350 K in ultrahigh vacuum. An integral inchworm‐like sample translation device avoids problems with unreliability and lock‐up by using clamping elements which have an unusually large range of motion. The entire STM, including the sample and the tip, are held isothermal. Temperature drift is less than 0.1 Å/min. A set temperature may be maintained, within 2°, for over 10 h. Operation of the instrument is demonstrated with an image of the Si(001) surface recorded at 120 K.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Diamond force microscope tips fabricated by chemical vapor deposition

G. J. Germann, G. M. McClelland, Y. Mitsuda, M. Buck, and H. Seki

Rev. Sci. Instrum. 63, 4053 (1992); http://dx.doi.org/10.1063/1.1143265 (3 pages) | Cited 12 times

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A chemical vapor deposition method is described for fabricating force microscope cantilevers with single‐crystal diamond tips. The ≂1‐μm‐diam diamond tips have corner radii of 30 nm, and have been used to study diamond–diamond friction on well‐characterized surfaces in UHV. The tip size and orientation can be determined by electron microscopy without altering the surface atomic structure.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
68.37.-d Microscopy of surfaces, interfaces, and thin films

An automatic field‐emission tip conditioning system

Shengyang Ruan and Oscar H. Kapp

Rev. Sci. Instrum. 63, 4056 (1992); http://dx.doi.org/10.1063/1.1143211 (5 pages) | Cited 2 times

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An automatic system has been completed for conditioning cold field‐emission tips to obtain high flux density and low‐noise emission. It was designed as a real‐time control and operating system for the electron source of a new sextupole‐corrected scanning transmission electron microscope and is able to condition the tip in situ. All of the control devices in this system are interfaced to a computer and communication across the electric field created by the 200‐kV acceleration voltage is accomplished with light pipes. A program, written in Pascal, controls the conditioning process. This system has been utilized to experimentally determine the optimal flash level for a newly fabricated tip as well as performing corrective maintenance to the conditioned tip to extend its maximum useful lifetime.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.07.Mp Transducers
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation

A micropipette force probe suitable for near‐field scanning optical microscopy

Shmuel Shalom, Klony Lieberman, Aaron Lewis, and Sidney R. Cohen

Rev. Sci. Instrum. 63, 4061 (1992); http://dx.doi.org/10.1063/1.1143212 (5 pages) | Cited 58 times

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In this paper it is demonstrated that glass micropipettes have unique applicability as force probes for a variety of imaging conditions and a variety of scanned tip microscopies. These probes are characterized in terms of the parameters that determine their force characteristics. Measurements are presented showing that one can readily achieve force constants of 10 N/m and it is anticipated that a reduction in this force constant by two orders of magnitude can be achieved. Such probes can be produced simply with a variety of geometries that permit a wide range of force imaging requirements to be met. Specifically, the glass micropipette probes reported in this paper are readily produced with apertures at the tip and can thus be applied to near‐field scanning optical microscopy (NSOM). This opens the possibility of the long‐awaited development of a universal feedback mechanism for NSOM.
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07.60.Pb Conventional optical microscopes
07.07.Mp Transducers

Scan system for the sextupole‐corrected scanning transmission electron microscopy

Shengyang Ruan and Oscar H. Kapp

Rev. Sci. Instrum. 63, 4066 (1992); http://dx.doi.org/10.1063/1.1143213 (5 pages) | Cited 4 times

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A computer‐controlled scan system has been completed for a sextupole‐corrected high‐resolution Scanning Transmission Electron Microscope. It is capable of driving 24 coils and 2 sextupoles in the microscope for beam scan, unscan, alignment, and correction of aberration. A PC‐AT is employed to manage this system and control the system devices. By means of these devices the raster size, shape, rotation angle, and dc offset can be controlled by subroutines for image generation/transformation. Computer control provides numerous advantages for the management of such a complicated system making it possible to modify many parameters and invoke a new group of settings simultaneously. This provides convenience in microscope operation for such functions as change in magnification, selection of viewing area, locations of objects of interest and montage.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Systematic procedures for atom‐probe field‐ion microscopy studies of grain boundary segregation

B. W. Krakauer and D. N. Seidman

Rev. Sci. Instrum. 63, 4071 (1992); http://dx.doi.org/10.1063/1.1143214 (9 pages) | Cited 29 times

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A procedure is presented for systematically and reproducibly preparing alloy specimens for the study of grain boundary (GB) segregation employing both transmission electron (TEM) and atom‐probe field‐ion microscopies (APFIM) to examine the same GB; the procedure is illustrated for an Fe(Si) alloy. A commercially available oxygen plasma source is incorporated in the sample preparation procedure to remove all traces of hydrocarbon build‐up introduced during TEM GB analysis, thus allowing controlled backpolishing after a TEM analysis. Specifications for the optimum tip geometry, i.e., how a GB is positioned in a tip via backpolishing to maximize the probability of its observation and subsequent compositional analysis via APFIM, are empirically determined: 30–200 nm for the GB‐to‐tip separation, and 40–80 nm for the GB diam for shank angles less than 20°. It is demonstrated that accurate quantitative APFIM analyses of an Fe‐3 at. % Si alloy are possible for pulse fractions ≥15% and specimen temperatures ≤55 K. Results are presented for a Σ≊3a GB that was first analyzed via TEM to determine its five macroscopic degrees of freedom, and then analyzed via APFIM to measure an average GB segregation enhancement factor for Si of 3.51±0.34 at 823 K.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
68.37.Vj Field emission and field-ion microscopy

Scanning surface harmonic microscopy: Scanning probe microscopy based on microwave field‐induced harmonic generation

B. Michel, W. Mizutani, R. Schierle, A. Jarosch, W. Knop, H. Benedickter, W. Bächtold, and H. Rohrer

Rev. Sci. Instrum. 63, 4080 (1992); http://dx.doi.org/10.1063/1.1143215 (6 pages) | Cited 25 times

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A scanning probe microscope has been integrated into a microwave resonator tunable from 2.2 to 3.4 GHz with a quality factor Q larger than 1000. Nonlinear phenomena caused generation of higher harmonics when rf fields in the range of 109 V/m were applied between tip and sample. Higher harmonic signals were detected at a bandwidth of 10 kHz on conductor surfaces as well as on thin insulating films and were used as feedback to the control loop for imaging graphite surface features and oxidized silicon surfaces with subnanometer resolution.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

A high‐power, power‐modulated TEA CO2 laser system as a driving source of electrostatic plasma waves

Koichi Sasaki, Kouichi Takahashi, Takaharu Fujii, Masaaki Nagatsu, and Takashige Tsukishima

Rev. Sci. Instrum. 63, 4086 (1992); http://dx.doi.org/10.1063/1.1143216 (6 pages) | Cited 1 time

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A high‐power, power‐modulated transversely excited atmosphere (TEA) CO2 laser system is developed with the intention of applying it to high‐temperature plasmas for diagnostic purpose. Two‐mode pulse injection locking is adopted to obtain the required output pulses of the TEA CO2 laser. Together with the power modulation, the gain‐switched spike of the output pulses are also suppressed by the adopted method, resulting in pulse lengthening. Two feedback loops are incorporated for reliable power modulation. The power‐modulated output so obtained is used to excite electrostatic plasma waves in laboratory plasmas.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
52.38.-r Laser-plasma interactions
42.60.Fc Modulation, tuning, and mode locking

A relatively simple way to produce THz bursts of optical pulses

D. L. MacFarlane and V. Narayan

Rev. Sci. Instrum. 63, 4092 (1992); http://dx.doi.org/10.1063/1.1143217 (4 pages) | Cited 6 times

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We present the design, construction, and demonstration of a device to produce short, high‐frequency bursts of ultrashort optical pulses. Specifically, we use a folded delay line structure called the optical rattler to produce a 600‐GHz burst of 400‐fs pulses.
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42.79.Hp Optical processors, correlators, and modulators
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Digital spectropolarimeter for the measurement of optical polarization

H. J. Lozykowski, T. Li, and Z. I. Akir

Rev. Sci. Instrum. 63, 4096 (1992); http://dx.doi.org/10.1063/1.1143218 (6 pages) | Cited 2 times

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A computerized setup for optical polarization measurements is described. The heart of this setup is a photoelastic modulator (PEM) whose retardation phase can be kept constant when the wavelength of modulated light is scanned in a wide range, and a dual‐channel gated photon counter which has the capability of compensating the variation of excitation intensity with time and wavelength. Unlike conventional analog setups, where the difference of two perpendicularly polarized light components (I+ − I−) and the average of these components 1/2(I+ + I−) are extracted electronically and the ratio 2(I+ − I−)/(I+ + I−) is recorded as degree of polarization, this spectropolarimeter directly records the I+ and I− components (for circular polarization) or I∥ and I⊥ components (for linear polarization) of the analyzed light signal. Once the spectra of the two components are stored as a numerical file in the computer, they can be processed to extract the degree of polarization as a function of wavelength, temperature, etc. The curvature and asymmetry of the modulator response are taken into account exactly in data processing. The spectropolarimeter has proved to be very accurate due to the capability of compensating the fluctuation in excitation source and of electronically tracking the modulation wavelength.
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07.60.Fs Polarimeters and ellipsometers
42.25.Ja Polarization

Performances of large multilayer mirrors for the 0.5–1.5 nm range

C. Khan Malek, T. Moreno, R. Barchewitz, R. Rivoira, and Y. Lepêtre

Rev. Sci. Instrum. 63, 4102 (1992); http://dx.doi.org/10.1063/1.1143219 (6 pages) | Cited 1 time

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6‐in.‐diam multilayer mirrors were fabricated for a double mirror monochromator designed to select photon energies between 830 and 1240 eV (0.5–1.5 nm). Coatings with 50 and 40 Mo/C bilayers with a bilayer d spacing of 4.1 and 4.6 nm, respectively, and a division parameter of Γ=0.44, were deposited by the triode sputtering method on 6‐in.‐diam silicon with 5% d uniformity. Similar coatings were also deposited on 2 in. silicon wafers. Peak reflectivity and integrated reflectivities were measured at several wavelengths between 0.5 and 1.5 nm using monochromatized synchrotron radiation. Measurements were performed along a 4 in. diameter for the large area coatings. The resolving power as measured in the center of the six inch mirrors was found to be 41 and 46 at 826 and 1240 eV, respectively, which compares well with the corresponding theoretical values of 43 and 40. The performance of a matched pair of multilayer mirrors with the smaller areas in the double mirror configuration was experimentally investigated as well. Reflectivity values for the two mirror configuration scheme were calculated from the experimental data for the individual mirrors. Possible applications of such monochromator in lithography research are briefly described.
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42.79.Bh Lenses, prisms and mirrors
07.85.-m X- and γ-ray instruments
41.85.Si Particle beam collimators, monochromators

A new Fourier transform millimeter wave spectrometer

R. Schwarz, A. Guarnieri, J.‐U. Grabow, and J. Doose

Rev. Sci. Instrum. 63, 4108 (1992); http://dx.doi.org/10.1063/1.1143220 (4 pages) | Cited 4 times

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We present the details of a new type of spectrometer which allows the recording of molecular emission signals in the microwave and millimeter wave region with subsequent Fourier transformation. First experiments up to 49 GHz have been carried out, but we claim that the biphase modulator used to 49 GHz will allow broadbanded spectroscopy up to the 100‐GHz region.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers
07.90.+c Other topics in instruments, apparatus, and components common to several branches of physics and astronomy (restricted to new topics in section 07)
42.65.-k Nonlinear optics

Electron optical analysis of a high‐resolution electron energy loss spectrometer with a retarding Wien filter

K. Tsuno

Rev. Sci. Instrum. 63, 4112 (1992); http://dx.doi.org/10.1063/1.1143221 (10 pages) | Cited 4 times

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The transfer matrix up to the second‐order aberrations has been formulated for an electron optical systems of a monochromator and an energy analyzer. Both of these instruments have two magnetic round lenses and a retarding Wien filter. The filter consists of a deceleration lens, a Wien filter, and an acceleration lens. The optimum excitation of the round lens is found to be that which provides parallel exit of electrons from the acceleration lens. The excitation of the Wien filter must be adjusted to focus the beam on the slit. The computed results are useful for finding the optimum operating conditions and for explaining experimental results of the high‐resolution electron energy loss spectrometer.  
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
79.60.-i Photoemission and photoelectron spectra
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Dielectric waveguide spectrometer for absorption spectroscopy of reactive vapors at microwave frequencies

I. Longo

Rev. Sci. Instrum. 63, 4122 (1992); http://dx.doi.org/10.1063/1.1143222 (6 pages)

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Experiments of microwave spectroscopy of gases at low pressures are performed with some advantages using dielectric waveguide cells. The construction of an improved version of a dielectric waveguide spectrometer is described. Details on the experimental methods utilized for gas handling and for the observation of some absorption lines of HNO3, O3, and H2O in the 18–26.5‐GHz frequency band, and of the CS radical at 49 GHz are given.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

A Bonse–Hart ultrasmall angle x‐ray scattering instrument employing synchrotron and conventional x‐ray sources

Benjamin Chu, Yingjie Li, and Tong Gao

Rev. Sci. Instrum. 63, 4128 (1992); http://dx.doi.org/10.1063/1.1143223 (6 pages) | Cited 9 times

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A Bonse–Hart ultrasmall angle x‐ray scattering (USAXS) instrument employing both synchrotron and conventional x‐ray sources was constructed. The instrument could be used to determine the structure of systems with inhomogeneity sizes on the order of ∼1000 nm. The characteristics of the instrument by using synchrotron and conventional x‐ray sources were compared. The use of synchrotron radiation showed much improved features not only in scattered intensity, but also in angular resolution. The scattered intensity was increased by a factor of about 20. Therefore weaker scattering systems could be investigated. By using the synchrotron radiation, the deficiency of the Bonse–Hart camera could be compensated. An angular scan containing ∼30 data points in the scattering angle region smaller than ∼2 mrad with reasonable signal‐to‐noise ratio could be completed within 5–10 min for samples with reasonable scattering power. Therefore, kinetic studies could be possible if the half time of structural development in a system is of the order of hours. For static experiments, a conventional x‐ray source could be used more conveniently to obtain a scattering curve with similar quality as that by means of synchrotron radiation partially because the channel‐cut crystals were not optimized for the synchrotron beam divergence and partially because alignments could be accomplished at a more leisurely pace using the conventional x‐ray source.
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07.85.-m X- and γ-ray instruments
61.05.cc Theories of x-ray diffraction and scattering
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

A new method for x‐ray powder diffraction studies

M. A. Beno, G. S. Knapp, and G. Jennings

Rev. Sci. Instrum. 63, 4134 (1992); http://dx.doi.org/10.1063/1.1143224 (4 pages) | Cited 6 times

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A new method has been developed which results in a major improvement in count rate of Bragg–Brentano‐type diffractometers. The method uses a focusing exit beam monochromator and a multichannel detector to achieve this improvement. The method is very efficient in eliminating background and can have very high resolution. Existing diffractometers can be easily modified to take advantage of this technique.
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07.85.-m X- and γ-ray instruments
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Application of molecular beam mass spectrometry to chemical vapor deposition studies

W. L. Hsu and D. M. Tung

Rev. Sci. Instrum. 63, 4138 (1992); http://dx.doi.org/10.1063/1.1143225 (11 pages) | Cited 41 times

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A molecular beam mass spectrometer system has been designed and constructed for the specific purpose of measuring the gaseous composition of the vapor environment during chemical vapor deposition of diamond. By the intrinsic nature of mass analysis, this type of design is adaptable to a broad range of other applications that rely either on thermal‐ or plasma‐induced chemical kinetics. When gas is sampled at a relatively high process pressure (∼2700 Pa for our case), supersonic gas expansion at the sampling orifice can cause the detected signals to have a complicated dependence on the operating conditions. A comprehensive discussion is given on the effect of gas expansion on mass discrimination and signal scaling with sampling pressure and temperature, and how these obstacles can be overcome. This paper demonstrates that radical species can be detected with a sensitivity better than 10 ppm by the use of threshold ionization. A detailed procedure is described whereby one can achieve quantitative analysis of the detected species with an accuracy of ±20%. This paper ends with an example on the detection of H, H2, CH3, CH4, and C2H2 during diamond growth.
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07.75.+h Mass spectrometers
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

A high‐flux atomic oxygen source for the deposition of high Tc superconducting films

L. S. Yu‐Jahnes, W. T. Brogan, Alfredo C. Anderson, and M. J. Cima

Rev. Sci. Instrum. 63, 4149 (1992); http://dx.doi.org/10.1063/1.1143226 (5 pages) | Cited 10 times

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A high‐flux atomic oxygen source has been developed for the deposition of in situ superconducting high Tc films under conditions that require low chamber pressures (≤10−4 Torr). The source uses a remote microwave plasma to generate the atomic species and is capable of producing an atomic oxygen flux greater than 2×1016 cm−2 s−1. The O2 dissociation efficiency of the atomic oxygen source is measured to be approximately 25%–30% for an O2 flow of 5 sccm. This high efficiency is achieved by the combined effects of a boric acid surface treatment to minimize recombination on the quartz tube and the addition of N2 to the oxygen plasma to increase the atomic oxygen yield. We have developed a treatment for the quartz surface that gives reproducible atomic oxygen flux with no degradation of the surface coating with repeated usage.
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74.78.-w Superconducting films and low-dimensional structures
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Superconducting re‐entrant cavity transducer for a resonant bar gravitational radiation antenna

N. P. Linthorne and D. G. Blair

Rev. Sci. Instrum. 63, 4154 (1992); http://dx.doi.org/10.1063/1.1143227 (7 pages) | Cited 7 times

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A 10‐GHz superconducting niobium re‐entrant cavity parametric transducer was developed for use in a cryogenic 1.5‐tonne Nb resonant bar gravitational radiation antenna. The transducer has a very high electrical Q (6×105 at 4.2 K), and was operated at high cavity fields without degrading the Q. A very high electromechanical coupling between the antenna and the transducer was therefore achieved. The highest coupling attained, constrained by the available pump power, was 0.11. If the transducer were to be operated in conjunction with a wideband impedance matching element, an antenna bandwidth comparable to the frequency of the antenna would be attained. The temperature dependence of the Q of the transducer was in good agreement with theory. At temperatures above about 6 K the Q was degraded by the increase in the BCS surface resistance, while at lower temperatures the Q was limited by radiative losses.
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04.80.-y Experimental studies of gravity
07.50.-e Electrical and electronic instruments and components

Three‐dimensional localization system for small magnetic dipoles

F. Incardona, L. Narici, I. Modena, and S. N. Ernè

Rev. Sci. Instrum. 63, 4161 (1992); http://dx.doi.org/10.1063/1.1143228 (6 pages) | Cited 5 times

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We developed a system for localizing orthogonal triplets of small magnetic dipoles with an array of magnetometers. These triplets can be used to measure, in quasi‐real time, the position of an object. This system is particularly useful when used with superconducting biomagnetic multichannel detectors. We present here a complete numerical simulation of the system performances and the first experimental tests with a biomagnetic detector (an array of 37 superconducting magnetometers). This system can be operated at frequencies outside the range of interest for biomagnetic measurements (that is typically 10−2–103 Hz). It features an accuracy of ±0.3 cm driving the triplet at a field intensity ≊10−12 T. The speed of the algorithm allows for quasi‐real‐time operation (t ∼ 10−1 s).
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87.50.C- Static and low-frequency electric and magnetic fields effects
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.55.-w Magnetic instruments and components
85.25.Dq Superconducting quantum interference devices (SQUIDs)

Hot wire anemometer operating at cryogenic temperatures

B. Castaing, B. Chabaud, and B. Hébral

Rev. Sci. Instrum. 63, 4167 (1992); http://dx.doi.org/10.1063/1.1143229 (7 pages) | Cited 7 times

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A micronic‐size hot wire anemometer operating at cryogenic temperatures (4 K) has been developed; using superconducting and resistive thin films, its electrical resistance is very sensitive to the velocity of a gaseous 4He subsonic jet. The fabrication procedure is described and the measured characteristics are compared with a simple thermal equilibrium model.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
47.80.-v Instrumentation and measurement methods in fluid dynamics
67.90.+z Other topics in quantum fluids and solids (restricted to new topics in section 67)

Contact potential measurement: Spacing‐dependence errors

Frank Rossi

Rev. Sci. Instrum. 63, 4174 (1992); http://dx.doi.org/10.1063/1.1143230 (8 pages) | Cited 15 times

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We examine the causes of spacing dependence of the nulling bias voltage in the vibrating capacitor contact potential measurement technique. In addition to effects already recognized in the literature, namely, nonuniform work functions, nonparallel surfaces, fringe fields, and capacitive coupling to distant surfaces, we investigate the effects of finite gain and spurious signals in feedback loop systems. We argue that much of the spacing dependence reported in the literature may be due to microphonic signals, which are very difficult to eliminate. We also discuss the means by which existing spacing dependence can be minimized.
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07.50.-e Electrical and electronic instruments and components
73.40.Cg Contact resistance, contact potential
73.30.+y Surface double layers, Schottky barriers, and work functions

Absolute ultrasonic displacement amplitude measurements with a submersible electrostatic acoustic transducer

William T. Yost and John H. Cantrell

Rev. Sci. Instrum. 63, 4182 (1992); http://dx.doi.org/10.1063/1.1143231 (7 pages) | Cited 12 times

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An experimental technique for absolute measurement of ultrasonic wave particle displacement amplitudes in liquids is reported. The technique is capable of measurements over a frequency range of two decades with a sensitivity less than one angstrom. The technique utilizes a previously reported submersible electrostatic acoustic transducer (ESAT) [Rev. Sci. Instrum. 50, 31 (1979)] featuring a conductive membrane stretched over a recessed electrode. An uncertainty analysis shows that the displacement amplitude of an ultrasonic plane wave incident on the ESAT can be experimentally determined to better than 2.3%–4%, depending on frequency, in the frequency range of 0.5–15 MHz. Membranes with lower and more uniform areal densities can improve the accuracy and extend the operation to higher frequencies.
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07.07.Mp Transducers
43.38.Bs Electrostatic transducers
43.58.Vb Calibration of acoustical devices and systems
62.60.+v Acoustical properties of liquids
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