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Feb 2000

Volume 71, Issue 2, pp. 335-1239

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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

A novel method to characterize photorefractive damage in quasiphase-matched wavelength converters

C. Q. Xu, H. Okayama, and Y. Ogawa

Rev. Sci. Instrum. 71, 335 (2000); http://dx.doi.org/10.1063/1.1150203 (3 pages) | Cited 1 time

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A novel two-beam method is proposed and applied for the first time, to characterize photorefractive damage (PRD) in a LiNbO3 quasiphase-matched (QPM) wavelength converter. In the proposed method, irradiation light from a Ti sapphire laser and a broadband probe beam from an erbium-doped fiber amplifier are coupled into a LiNbO3 QPM waveguide. The PRD effect caused by the irradiation is studied by monitoring the generated second-harmonic light spectrum of the probe light. It is shown that PRD in the LiNbO3 QPM waveguide can be qualitatively characterized by the proposed method, and relevant information relating to the QPM wavelength conversion can be extracted directly. © 2000 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Lossless beam combiners for nearly equal laser frequencies

D. Haubrich, M. Dornseifer, and R. Wynands

Rev. Sci. Instrum. 71, 338 (2000); http://dx.doi.org/10.1063/1.1150204 (3 pages) | Cited 3 times

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We discuss three ways to combine two laser beams with equal linear polarizations and very closely spaced frequencies into a single output beam containing up to 100% of the input power of each beam. One setup, a modified Mach–Zehnder interferometer, is examined in detail; it allows to adjust the combined output power electronically with the help of a simple servo loop. With off-the-shelf optical components we obtained a 98% efficiency. © 2000 American Institute of Physics.
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42.79.Fm Reflectors, beam splitters, and deflectors
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
07.60.Ly Interferometers
42.79.Ci Filters, zone plates, and polarizers

Laser frequency stabilization using linear magneto-optics

Valeriy V. Yashchuk, Dmitry Budker, and John R. Davis

Rev. Sci. Instrum. 71, 341 (2000); http://dx.doi.org/10.1063/1.1150205 (6 pages) | Cited 46 times

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The design of a diode laser frequency stabilization system using the Zeeman effect is described. Various regimes of operation are analyzed using the Jones matrix approach. The system is different from the original Joint Institute for Laboratory Astrophysics design in that the magnetic fields are fully contained and thus it can be used in proximity of magnetically sensitive instruments. © 2000 American Institute of Physics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
85.70.Sq Magnetooptical devices

A laser-locked cavity ring-down spectrometer employing an analog detection scheme

T. G. Spence, C. C. Harb, B. A. Paldus, R. N. Zare, B. Willke, and R. L. Byer

Rev. Sci. Instrum. 71, 347 (2000); http://dx.doi.org/10.1063/1.1150206 (7 pages) | Cited 44 times

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A system is described that employs a diode-pumped Nd:YAG continuous-wave laser source servolocked to a three-mirror optical cavity and an analog detection circuit that extracts the ring-down rate from the exponentially decaying ring-down waveform. This scheme improves on traditional cavity ring-down spectroscopy setups by increasing signal acquisition rates to tens of kilohertz and reducing measurement noise sources. For example, an absorption spectrum of a weak CO2 transition at 1064 nm is obtained in less than 10 s at a spectral resolution of 75 kHz employing a cavity with an empty-cavity ring-down decay lifetime of 2.8 μs and a total roundtrip path length of 42 cm. The analog detection system enables laser frequency scan rates greater than 500 MHz/s. The long-term sensitivity of this system is 8.8×10−12 cm−1 Hz−1/2 and the short-term sensitivity is 1.0×10−12 cm−1 Hz−1/2. © 2000 American Institute of Physics.
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07.60.Rd Visible and ultraviolet spectrometers
42.62.Fi Laser spectroscopy
85.60.Gz Photodetectors (including infrared and CCD detectors)

Time-correlated photon counting technique robust against multiple photon events using a multianode photomultiplier tube

Shinji Ohsuka, Akira Ohsugi, and Hisayoshi Takamoto

Rev. Sci. Instrum. 71, 354 (2000); http://dx.doi.org/10.1063/1.1150207 (7 pages)

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A time-correlated photon counting technique which is robust against multiple photon events has been developed. Utilizing a 16 channel multianode photomultiplier tube, both the time interval between the excitation and the first detection of a fluorescence photon and the number of detected fluorescence photons are measured simultaneously. Based on the time and the number data fluorescence decay parameters can be estimated by maximizing the log likelihood. Results of computer simulations and experiments show that this technique can be successfully applicable at high detection rates of >0.9 fluorescence photon detection event per excitation on average. © 2000 American Institute of Physics.
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07.60.Dq Photometers, radiometers, and colorimeters
85.60.Ha Photomultipliers; phototubes and photocathodes

Data acquisition card for fluctuation correlation spectroscopy allowing full access to the detected photon sequence

John S. Eid, Joachim D. Müller, and Enrico Gratton

Rev. Sci. Instrum. 71, 361 (2000); http://dx.doi.org/10.1063/1.1150208 (8 pages) | Cited 15 times

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Typically, fluctuation correlation spectroscopy (FCS) data acquisition cards measure the number of photon events per time interval (i.e., bin)—time mode. Commercial FCS cards combine the bins through hardware in order to calculate the autocorrelation function. Such a design therefore does not yield the time resolved photon sequence, but only the autocorrelation of that sequence. A different acquisition method which measures the number of time intervals between photon events has been implemented—photon mode. This method takes advantage of the fact that in FCS the rate of photon counts is much less than the frequency of the clock that is used to determine the temporal location of the photons. By using this new mode of data acquisition, the current card design allows for 25 ns time resolution. The data acquisition card can operate in both time and photon mode and yields the time resolved sequence of photon arrivals in both cases. Therefore, the data is available for analysis by any method(s), such as but not limited to, autocorrelation, photon counting histogram, and higher order autocorrelation. © 2000 American Institute of Physics.
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07.60.Rd Visible and ultraviolet spectrometers
07.05.Hd Data acquisition: hardware and software
42.79.Hp Optical processors, correlators, and modulators
back to top CHARGED PARTICLE SOURCES, OPTICS and ACCELERATION

Toward the experimental observation of nonlinear effects in laser-electron beam scattering

Koji Matsukado, Ichita Endo, Tohru Takahashi, and Toshiaki Tauchi

Rev. Sci. Instrum. 71, 369 (2000); http://dx.doi.org/10.1063/1.1150209 (7 pages) | Cited 1 time

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We constructed an experimental system to observe nonlinear effects in the Compton scattering. The electron beam is supplied by an electron gun and a photon beam comes from a table-top tera-watt laser system. As a test experiment, we measured the Compton scattering in linear regime and had a good agreement with simulations, indicating that the background level of the system was under control and the detection efficiency was well estimated. The simulation study shows that it is necessary to use a laser beam with an inclined polarization plane to obtain a maximal amount of second harmonics in photon-electron scattering. © 2000 American Institute of Physics.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
41.75.Fr Electron and positron beams
42.25.Fx Diffraction and scattering

Pulsed magnetic quadrupole lenses for high rigidity beams

G. Li, U. Czok, A. Kalimov, M. Winkler, and H. Wollnik

Rev. Sci. Instrum. 71, 376 (2000); http://dx.doi.org/10.1063/1.1150210 (4 pages) | Cited 1 time

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New pulsed magnetic quadrupole lenses have been developed that can be used to focus pulsed ion beams of high rigidity. To reach sufficiently high flux densities we built such quadrupole lenses as optimized steel-free devices. Up to now a flux density of ≈ 12 T has been reached in a quadrupole of 22 mm aperture with a sufficient field quality. This value is higher than or comparable to values reached in superconducting quadrupole lenses or in pulsed plasma lenses. © 2000 American Institute of Physics.
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41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles

Production of radioactive ion beams using the in-flight technique

B. Harss, R. C. Pardo, K. E. Rehm, F. Borasi, J. P. Greene, R. V. F. Janssens, C. L. Jiang, J. Nolen, M. Paul, J. P. Schiffer, R. E. Segel, J. Specht, T. F. Wang, P. Wilt, and B. Zabransky

Rev. Sci. Instrum. 71, 380 (2000); http://dx.doi.org/10.1063/1.1150211 (8 pages) | Cited 25 times

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Reactions with a heavy projectile incident on a light target can be used for the efficient in-flight production of secondary radioactive beams. An overview of this technique is given using data on 17F beams produced via the p(17O, 17F)n and d(16O, 17F)n reactions. With primary 16,17O beam currents of 100 pnA, intensities of up to 2×106 17F/s on target were achieved. Using this beam, the p(17F,α)14O reaction was measured. © 2000 American Institute of Physics.
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29.25.Rm Sources of radioactive nuclei
29.25.Ni Ion sources: positive and negative

High current, low pressure plasma cathode electron gun

Dan M. Goebel and Ron M. Watkins

Rev. Sci. Instrum. 71, 388 (2000); http://dx.doi.org/10.1063/1.1150212 (11 pages) | Cited 24 times

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A plasma-cathode electron gun based on a moderate pressure (>5 mTorr) cold-cathode discharge and a high perveance, multiaperture accelerator was previously developed at Hughes Research Laboratories and produced electron beam currents of up to 1 kA at voltages of over 200 kV for pulse lengths of 100 μs. This gun was limited in pulse repetition frequency and duty by the gas-puff system that provided adequate gas pressure in the hollow cathode to operate the glow discharge while keeping the pressure in the beam transport region sufficiently low. We describe a new plasma cathode electron gun (PCE gun) that eliminates this problem by replacing the glow-discharge plasma generator in the electron gun by a low-pressure thermionic discharge in a magnetic multipole confinement chamber. Proper design of the plasma generator and electrical circuit provides high electron-current densities to the accelerator structure at very low gas pressure (<10−4 Torr). The static gas pressure permits the pulse repetition frequency to be very high (>1.5 kHz demonstrated) with electron beam currents up to 200 A at voltages up to 120 kV demonstrated. The design and performance of the PCE gun, along with several models used to predict and scale the performance, are discussed. © 2000 American Institute of Physics.
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29.25.Bx Electron sources
52.75.-d Plasma devices
07.77.Ka Charged-particle beam sources and detectors
84.47.+w Vacuum tubes
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Pneumatic repetitive injector with a porous pellet generator for steady-state plasma fueling

I. Viniar and S. Sudo

Rev. Sci. Instrum. 71, 399 (2000); http://dx.doi.org/10.1063/1.1150213 (4 pages)

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A repetitive injector with a new porous pellet generator providing steady-state plasma fueling has been developed for fusion devices. The pellet generator can produce an unlimited number of pellets at 0.5–0.9 Hz. Several thousands of hydrogen pellets of 2.5 mm diameter and 2–4 mm length were formed in different modes and accelerated to 0.8–1.1 km/s with an average 70% reliability. The pellet generator has no moving units and contains only 3–5 pellets as reserve fuel for steady-state operation, so the injector design is compatible with and attractive for future tritium operation. A detailed design description and test results are presented. © 2000 American Institute of Physics.
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28.52.Cx Fueling, heating and ignition

Effect of harmonic rf fields on the emissive probe characteristics

T. Lho, N. Hershkowitz, and G-H. Kim

Rev. Sci. Instrum. 71, 403 (2000); http://dx.doi.org/10.1063/1.1150214 (3 pages) | Cited 3 times

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New features of the emissive probe characteristic curves in an inductive plasma source were observed in the E mode operation. More than the two inflection points in the derivative of the I–V characteristic curves are found when the harmonics of the input frequency (13.56 MHz) are present. The pairs of inflection points are symmetric about dc plasma potential. © 2000 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
back to top BASIC PHENOMENA

Spatio-temporal measurements of Trichel corona discharge using capacitive probe diagnostic

Deepak K. Gupta, H. Ramachandran, and P. I. John

Rev. Sci. Instrum. 71, 406 (2000); http://dx.doi.org/10.1063/1.1150215 (7 pages) | Cited 1 time

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A nonintrusive capacitive probe diagnostic is developed to estimate the spatio-temporal charge density variation of corona discharge. Tikhonov regularization is used to calculate the charge density from measured potential. A good time resolution and restricted space resolution in charge density is achieved. The axial electric field due to space charge is also estimated by considering the discharge to be of finite radius and with uniformly distributed charge density along the radial direction. Space charge wave front movement, as predicted by existing theories, is noticed. Constraints of present technique and scope for further improvements are discussed. © 2000 American Institute of Physics.
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52.80.Hc Glow; corona
52.70.Ds Electric and magnetic measurements
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Comparison between the discharge development in the two- and three-electrode spark gap switches

Hossein Golnabi

Rev. Sci. Instrum. 71, 413 (2000); http://dx.doi.org/10.1063/1.1150216 (7 pages) | Cited 1 time

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Results of numerical simulation of two- and three-electrode spark gaps operating with pure nitrogen gas are compared. Our result show that in both cases the discharge process evolves via two stages very similar to that was reported in nitrogen glow discharge studies. First, the primary electrons produce positive nitrogen ions; second, the produced ions can disturb the applied field, and can create the space charge region. The undulations observed are because of the secondary effects, in particular, the cathode-directed streamers. The delay time for the three-electrode spark gap is more than that of the two-electrode discharge. Current growth is faster for the two-electrode spark gap in comparison with the three-electrode one. The oscillations are more enhanced for the case of the three-electrode spark gap. Our simulation method provides both temporal and spatial information concerning the operation of such switches. The reported results are helpful in design and optimization of both the two- and three-electrode spark gaps. © 2000 American Institute of Physics.
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52.75.Kq Plasma switches (e.g., spark gaps)
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
back to top MICROSCOPY and IMAGING

Servomechanism for locking scanning tunneling microscope tip over surface nanostructures

K. J. Ito, Y. Uehara, S. Ushioda, and K. Ito

Rev. Sci. Instrum. 71, 420 (2000); http://dx.doi.org/10.1063/1.1150217 (4 pages) | Cited 8 times

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Measurement of the light emission spectrum from a scanning tunneling microscope (STM) requires a long exposure time due to its extremely low intensity, and thermal drift of the tip during the exposure time limits the spatial resolution. To improve the resolution, a computer controlled servomechanism that locks the STM tip over a target position has been developed. We have measured the light emission spectra from individual nanometer scale structures on an evaporated Au film with and without this mechanism, and demonstrated the effectiveness of the servomechanism. © 2000 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes
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
07.07.Tw Servo and control equipment; robots
68.35.B- Structure of clean surfaces (and surface reconstruction)

A low-temperature ultrahigh vacuum scanning tunneling microscope with a split-coil magnet and a rotary motion stepper motor for high spatial resolution studies of surface magnetism

O. Pietzsch, A. Kubetzka, D. Haude, M. Bode, and R. Wiesendanger

Rev. Sci. Instrum. 71, 424 (2000); http://dx.doi.org/10.1063/1.1150218 (7 pages) | Cited 45 times

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We present the design of a new ultrahigh vacuum scanning tunneling microscope (STM) which operates at T<20 K inside the bore of a 2.5 T superconducting split-coil magnet. The tip/sample region can easily be controlled visually, thus allowing safe and fast exchange of samples and tips while the microscope stays at low temperatures. A newly developed rotary motion stepper motor is presented which allows rotation of the sample by >270° about an axis perpendicular to the tip axis. This feature allows metal or molecular beam evaporation normal to the sample surface. Even more important, by means of this device tip and sample can be brought into a parallel or antiparallel magnetic configuration thus opening a novel approach to the study of magnetic phenomena on an atomic length scale. In addition, measurements of the magneto-optical Kerr effect can be carried out without removing the sample from the STM. Also a new tip exchange mechanism is described. The microscopic and spectroscopic performance of the new instrument is illustrated on Au(111)/mica, on Tb(0001)/W(110), and on Gd(0001)/W(110). © 2000 American Institute of Physics.
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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
75.70.Rf Surface magnetism
07.79.Cz Scanning tunneling microscopes
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
84.71.Ba Superconducting magnets; magnetic levitation devices
84.50.+d Electric motors
78.20.Ls Magneto-optical effects

Variable temperature fluid stage for atomic force microscopy

R. K. Workman and S. Manne

Rev. Sci. Instrum. 71, 431 (2000); http://dx.doi.org/10.1063/1.1150219 (6 pages) | Cited 7 times

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The design of a simple, variable temperature fluid cell for an atomic force microscope is presented. The stage is based on a thermoelectric heating/cooling element, which allows control of sample and fluid temperature from −5 to 130 °C. The stage is stable enough to image at molecular resolution almost throughout the range of accessible temperature and can be used for imaging in either gas or liquids. This allows the molecular scale investigation of surface phase transitions and chemical kinetics at solid/liquid interfaces by varying the temperature. As an example, we present results of temperature-induced phase transitions in self-assembled surfactant aggregates at solid/liquid interfaces. © 2000 American Institute of Physics.
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07.79.Lh Atomic force microscopes
06.60.Ei Sample preparation (including design of sample holders)
68.35.Rh Phase transitions and critical phenomena
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
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

Dynamics of a piezoelectric tuning fork/optical fiber assembly in a near-field scanning optical microscope

Konstantin B. Shelimov, Dmitri N. Davydov, and Martin Moskovits

Rev. Sci. Instrum. 71, 437 (2000); http://dx.doi.org/10.1063/1.1150220 (7 pages) | Cited 10 times

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Factors leading to a decrease in the resonance quality (the Q factor) of quartz microtuning fork/optical fiber assemblies used as sensing elements in near-field scanning optical microscopes were considered using a simple elastomechanical analysis. Experiments to test the predictions of the analysis were carried out and strategies for recovering high Q factors were proposed and tested. Three major factors affecting the magnitude of the Q factor are discussed. The first is the stiffness imparted to the tine of the microtuning fork by the optical fiber attached to it; the second is the location of the attachment point of the fiber along the tine; the third is the resonant vibrational excitation of the fiber tip which acts as an energy dissipative channel. For tapping mode operation using a standard 125 μm diameter fiber, the large longitudinal stiffness of the fiber results in a dramatic Q-factor degradation. This effect can be overcome by reducing the diameter of the fiber cladding, d, and by slightly bending the fiber. Under these conditions, bending rather than longitudinal stretching dominates the fiber dynamics. The effective bending force constant for a thinned fiber is predicted to be proportional to d4. A sharp upturn in the Q factor is observed for d ⩽ 25 μm, consistent with this prediction. The effective stiffness and mass of the fiber are also expected to scale approximately as x3, where x is the distance from the point of attachment of the fiber to the fork’s base. Hence, the Q factor can be improved further by attaching the fiber closer to the tuning fork’s base. Vibrational coupling between the tuning fork and the probe tip can result in a substantial Q-factor degradation for tips of a certain size. By taking these insights into consideration, we were able to construct tapping mode tuning fork/optical fiber assemblies with Q factors of up to 9000. © 2000 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.60.Vg Fiber-optic instruments
42.81.Pa Sensors, gyros
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Real time imaging of two-dimensional charge on dielectric surfaces

R. Budakian and S. J. Putterman

Rev. Sci. Instrum. 71, 444 (2000); http://dx.doi.org/10.1063/1.1150221 (6 pages) | Cited 1 time

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A technique has been developed to measure two-dimensional (2D) charge distributions on dielectric surfaces in real time. A thin layer of polymer-dispersed liquid crystal (PDLC) placed between a dielectric substrate and a conducting plane undergoes a transition from an opaque to a transparent state due to the electric field of the surface charge. The cell is uniformly illuminated from the front and the transmitted light, which is proportional to the local charge density, is imaged using a charge coupled device camera. Due to the finite resistivity of the liquid crystal, however, the static field from the charges must be modulated in time in order to produce a sustained transition inside the PDLC. The modulation is produced by placing a rotating metal chopper near the surface. The magnitude and sign of the charge are measured by calibrating the response of the PDLC to a series of bias voltages. The technique has been used to image surfaces as large as 3 mm×5 mm with 30 μm spatial resolution in 333 ms. © 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.)
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
42.79.Pw Imaging detectors and sensors
42.79.Kr Display devices, liquid-crystal devices
back to top CONDENSED MATTER; MATERIALS

Nuclear magnetic resonance spectrometer with a frequency range extended below the megahertz region

R. Sitnikov, I. Furó, U. Henriksson, and F. Tóth

Rev. Sci. Instrum. 71, 450 (2000); http://dx.doi.org/10.1063/1.1150222 (8 pages) | Cited 1 time

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A conventional nuclear magnetic resonance (NMR) spectrometer with an original low-frequency limit of 2 MHz and equipped with an electromagnet is rebuilt to allow performing NMR experiments at resonance frequencies down to 100 kHz. The instrument is intended for accurate field-dependent spin relaxation studies. The preamplifier and the duplexer are completely replaced by new designs that provide low noise figure, large gain and fast recovery. The receiver, the transmitter, and the magnet power supply are modified to operate at low frequency (receiver and transmitter) and at low current (power supply). The performance of the instrument is demonstrated by 2H NMR experiments in the 500 kHz–2 MHz region and is compared to that of instruments based on direct current-superconducting quantum interference device and operated on room-temperature samples. © 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

An efficient 8 T extraction vector magnetometer with sample rotation for routine operation

D. Dufeu, E. Eyraud, and P. Lethuillier

Rev. Sci. Instrum. 71, 458 (2000); http://dx.doi.org/10.1063/1.1150223 (4 pages) | Cited 4 times

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We describe here a fully automated system for magnetic anisotropy study operating in the field range ±8 T, between 1.8 and 300 K. The three components of the magnetization are simultaneously measured, using the flux extraction method, through three sets of orthogonal pickup coils. The sample is fixed on a rod which enables its vertical movement for the magnetization measurement and its rotation around a horizontal axis, perpendicular to the magnetic field, with a precision of about 1°. The sensitivity of the measurements is 10−7 A m2 along the vertical axis and 5×10−7 A m2 along the horizontal axes. © 2000 American Institute of Physics.
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07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Density-of-states effective mass and scattering parameter measurements by transport phenomena in thin films

D. L. Young, T. J. Coutts, and V. I. Kaydanov

Rev. Sci. Instrum. 71, 462 (2000); http://dx.doi.org/10.1063/1.1150224 (5 pages) | Cited 27 times

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A novel machine has been developed to measure transport coefficients in the temperature range of 50–350 K of thin films deposited on electrically insulating substrates. The measured coefficients—resistivity, Hall, Seebeck, and Nernst—are applied to solutions of the Boltzmann transport equation to give information about the film’s density-of-states effective mass, the Fermi energy level, and an energy-dependent scattering parameter. The machine is designed to eliminate or compensate for simultaneously occurring transport phenomena that would interfere with the desired measured quantity, while allowing for all four coefficients to be measured on the same sample. An average density-of-states effective mass value of 0.29±0.04me was measured on the transparent conductive oxide, cadmium stannate (CTO), over a carrier concentration range of 2–7×1020 cm−3. This effective mass value matched previous results obtained by optical and thermoelectric modeling. The measured scattering parameter indicates that neutral impurities or a mixture of scattering mechanisms may inhibit the transport of carriers in CTO. © 2000 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
73.50.Bk General theory, scattering mechanisms
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Lw Thermoelectric effects

Electron cyclotron resonance plasma source for ion assisted deposition of thin films

K. Deenamma Vargheese and G. Mohan Rao

Rev. Sci. Instrum. 71, 467 (2000); http://dx.doi.org/10.1063/1.1150225 (6 pages) | Cited 11 times

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An electron cyclotron resonance (ECR) plasma source (10 cm in diameter) has been developed for ion assisted sputter deposition of thin films. Variation of plasma parameters like ion density, electron temperature, plasma potential, and floating potential as a function of pressure and microwave power has been studied using Langmuir probe analysis. The ECR source gives an ion density of 1.01×1011/cm3 at a distance of 8 cm from the source exit at a pressure of 8×10−4 mbar and 400 W of microwave power. The uniformity of the plasma parameters at the substrate position was found to be ±2% over a diameter of 12 cm. Thin films of copper and silicon nitride have been deposited by rf sputtering in the presence of ECR plasma. The properties showed a significant change at an ECR power of 100 W. © 2000 American Institute of Physics.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.15.Cd Deposition by sputtering
52.50.Dg Plasma sources
29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Measurement of the complex dielectric constant down to helium temperatures. I. Reflection method from 1 MHz to 20 GHz using an open ended coaxial line

H. C. F. Martens, J. A. Reedijk, and H. B. Brom

Rev. Sci. Instrum. 71, 473 (2000); http://dx.doi.org/10.1063/1.1150226 (5 pages) | Cited 11 times

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The reflection off an open ended coaxial probe pressed against a material under test is used to determine the complex microwave (1 MHz–20 GHz) dielectric response of the material. A full-wave analysis of the aperture admittance of the probe, in terms of the dielectric properties of the backing material and the dimensions of the experimental geometry, is given. We discuss the calibration procedure of the setup and present the complex dielectric response of several materials determined from the measured reflection coefficient. The results obtained with the open ended coax interpolate well between data taken at lower and higher frequency bands using different experimental methods. We demonstrate that this method can be applied to perform dielectric measurements at cryogenic temperatures. © 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.)
84.40.Az Waveguides, transmission lines, striplines
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.68.+m Photography, photographic instruments; xerography

Measurement of the complex dielectric constant down to helium temperatures. II. Quasioptical technique from 0.03 to 1 THz

J. A. Reedijk, H. C. F. Martens, B. J. G. Smits, and H. B. Brom

Rev. Sci. Instrum. 71, 478 (2000); http://dx.doi.org/10.1063/1.1150227 (4 pages) | Cited 10 times

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A quasioptical method is described that allows the determination of the complex dielectric constant almost continuously in the millimeter wave regime without the use of electrical contacts. The technique allows the dielectric properties of bulk samples (solids, powders, and liquids) and thin films (free standing or deposited on a substrate) to be measured with excellent absolute accuracy down to 2 K. © 2000 American Institute of Physics.
Show PACS
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
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