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Jul 1999

Volume 70, Issue 7, pp. 2899-3187

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back to top CONDENSED MATTER; MATERIALS

Design and fabrication of a simple pneumatic loading attachment for diamond anvil cells

Ravhi S. Kumar, A. Sekar, N. Victor Jaya, and S. Natarajan

Rev. Sci. Instrum. 70, 3074 (1999); http://dx.doi.org/10.1063/1.1149869 (3 pages) | Cited 1 time

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A simple pneumatic pressure attachment has been designed and fabricated for Mao–Bell and National Bureau of Standard type diamond anvil cells (DACs). The assembly can be fitted to the lever arm of the DAC for applying pressure on the diamonds and the pressure at the sample site has been calibrated against the gas dial using the equation of state of silver loaded in the DAC. © 1999 American Institute of Physics.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
06.20.F- Units and standards

Rotating analyzer–fixed analyzer ellipsometer based on null type ellipsometer

Stoyan C. Russev and Tzanimir Vl. Arguirov

Rev. Sci. Instrum. 70, 3077 (1999); http://dx.doi.org/10.1063/1.1149870 (6 pages) | Cited 9 times

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The theory and design of an inexpensive rotating analyzer unit is presented, which allows a conventional null type ellipsometer to work as rotating analyzer–fixed analyzer automatic ellipsometer, without sacrificing the possibility to work in null mode. The mode switching is performed simply by adding or removing the rotating analyzer from its holder. It is shown that the rotating analyzer phase shift in rotating analyzer–fixed analyzer mode can be run-time determined from the measured Fourier coefficients. This avoids any need of recalibration procedure after mode switching and makes unnecessary plane of incidence synchronization, which further simplifies the needed hardware and reduces the errors connected with the phase shift instability of the output signal. The run-time phase shift calibration procedure and subsequent ellipsometric angles determination do not involve normalization of the output signal Fourier coefficients to the zeroth harmonic, eliminating in this way the influence of the dc component time drift. © 1999 American Institute of Physics.
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07.60.Fs Polarimeters and ellipsometers

Evanescent microwave probes on high-resistivity silicon and its application in characterization of semiconductors

M. Tabib-Azar, D. Akinwande, G. E. Ponchak, and S. R. LeClair

Rev. Sci. Instrum. 70, 3083 (1999); http://dx.doi.org/10.1063/1.1149871 (4 pages) | Cited 16 times

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In this article we report the design, fabrication, and characterization of very high quality factor 10 GHz microstrip resonators on high-resistivity (high-ρ) silicon substrates. Our experiments show that an external quality factor of over 13 000 can be achieved on microstripline resonators on high-ρ silicon substrates. Such a high Q factor enables integration of arrays of previously reported evanescent microwave probe (EMP) on silicon cantilever beams. We also demonstrate that electron–hole pair recombination and generation lifetimes of silicon can be conveniently measured by illuminating the resonator using a pulsed light. Alternatively, the EMP was also used to nondestructively monitor excess carrier generation and recombination process in a semiconductor placed near the two-dimensional resonator. © 1999 American Institute of Physics.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
84.40.Az Waveguides, transmission lines, striplines
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
07.68.+m Photography, photographic instruments; xerography

ac self-field loss measurement system

Lubomil Jansak

Rev. Sci. Instrum. 70, 3087 (1999); http://dx.doi.org/10.1063/1.1149872 (5 pages) | Cited 5 times

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The accuracy and reproducibility of a self-field ac loss measurement technique for high-temperature superconducting tapes using a digital lock-in amplifier are discussed. The influence of the reference phase setting on the error was calculated and verified experimentally for different degrees of inductive component compensation. We estimated that for precise ac loss measurements of uncompensated specimens it is necessary set the reference phase with the precision on the order of 0.001°. For a compensated sample a phase error of 0.1° is tolerable. The measurement error due to common-mode voltage was studied and its minimization is proposed. A test procedure for common-mode voltage error evaluation was also experimentally verified. Ideas for better performance of the measurement system are proposed. © 1999 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.)
84.30.Le Amplifiers
84.71.Mn Superconducting wires, fibers, and tapes
74.72.-h Cuprate superconductors

Mirror-image calibrator for resonant perturbation method in surface resistance measurements of high Tc superconducting thin films

C. K. Ong, Linfeng Chen, Jian Lu, S. Y. Xu, Xuesong Rao, and B. T. G. Tan

Rev. Sci. Instrum. 70, 3092 (1999); http://dx.doi.org/10.1063/1.1149893 (5 pages) | Cited 5 times

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In surface resistance measurement of high Tc superconducting (HTS) thin films, the conventional resonant perturbation methods have large uncertainties, because their calibrators usually have much larger surface resistance than HTS thin films. This article describes a new type of calibrator, mirror-image calibrator: when the open end of a dielectric resonator is connected to its mirror image, the resonant frequency and quality factor of the resonator are equal to those of the dielectric resonator when its open end is shorted by a perfect conductor. This principle is applied to modify the dielectric resonator method in surface resistance measurement of HTS thin films. The structures of the dielectric resonator for surface resistance measurement (Rs probe) and its mirror-image calibrator are explained in detail. Comparison is made between the present technique and the conventional perturbation technique, and results show that the accuracy and sensitivity of the resonant perturbation method are greatly improved by using the mirror-image calibrator. © 1999 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
06.20.F- Units and standards

Radio-frequency impedance measurements using a tunnel-diode oscillator technique

H. Srikanth, J. Wiggins, and H. Rees

Rev. Sci. Instrum. 70, 3097 (1999); http://dx.doi.org/10.1063/1.1149892 (5 pages) | Cited 26 times

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A resonant method based on a tunnel-diode oscillator for precision measurements of relative impedance changes in materials is described. The system consists of an effective self-resonant LC tank circuit driven by a forward-biased tunnel diode operating in its negative resistance region. Samples under investigation are placed in the core of an inductive coil and impedance changes are determined directly from the measured shift in resonance frequency. A customized low temperature insert is used to integrate this experiment with a commercial Model 6000 Physical Property Measurement System (Quantum Design). Test measurements on a manganese-based perovskite sample exhibiting colossal magnetoresistance indicate that this method is well suited to study the magnetoimpedance in these materials. © 1999 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.)
84.30.Ng Oscillators, pulse generators, and function generators
07.68.+m Photography, photographic instruments; xerography
75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials

Space charge measurement in a dielectric material after irradiation with a 30 kV electron beam: Application to single-crystals oxide trapping properties

B. Vallayer, G. Blaise, and D. Treheux

Rev. Sci. Instrum. 70, 3102 (1999); http://dx.doi.org/10.1063/1.1149887 (11 pages) | Cited 38 times

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When an insulating material is subjected to electron irradiation, it produces a secondary emission the yield of which varies from a few percent to very high values (up to 24 per incoming electron) depending on the material and the experimental conditions. If the secondary electron emission yield is less than one, a net negative charge remains trapped in the sample. In this case, the study of the electric charges trapping properties of the material becomes possible. This article describes how it is possible to use a secondary electron microscope (SEM) as a device to perform such a study. In Sec. II, the effect of a net negative trapped charge resulting (from the injection of typically 50 pC) on the imaging process of the SEM has been described. It has been shown that when the trapped charge is high enough, it acts as a mirror reflecting the incoming electron beam which is deflected somewhere in the vacuum chamber of the microscope. A global qualitative description of the image displayed on the screen is first presented. Then electron trajectories are quantitatively studied by using the Rutherford scattering cross section in the case of a point charge. When the charge is extended, a numeric simulation has been done in order to predict the validity range of the previous model. Once the trajectories have been calculated, the connection between the remarkable elements of the image and the quantity of trapped charges has been established. Moreover, this technique allows one to study the lateral dimension of the trapped charge zone and to measure the surface potential. In Sec. III, the discussion is first focused on some precautions to be taken concerning the sample preparation before the experiment is performed. It has been shown that surface defects due either to contamination layers or machining change the trapping properties of single-crystals ceramics such as MgO and Al2O3. A cleaning procedure is proposed that consists of annealing the sample at 1500 °C for 4 h in order to heal the crystalline defects and a heating at 400 °C in the vacuum chamber of the SEM to remove the contamination layers. Finally, the effect of the temperature on the trapping properties of pure and chromium doped sapphire has been studied in relation with the chromium concentration. It is shown that temperature behavior of trapping is in relation with the chromium concentration. In the pure sapphire trapping is activated below −16 °C, in 500 ppm rubis it is below −9.5 °C due to isolated chromium atoms, and in the 8000 ppm rubis the critical trapping temperature rises to 3.7 °C due to Cr3+ pairs. The interpretation of the role played by chromium on trapping is based on the experimental study of the fluorescence of chromium atoms and pairs as a function of concentration. © 1999 American Institute of Physics.
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77.22.Jp Dielectric breakdown and space-charge effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.80.Fe Electron and positron radiation effects
61.82.Ms Insulators
79.20.Hx Electron impact: secondary emission
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Automated, low-temperature dielectric relaxation apparatus for measurement of air-sensitive, corrosive, hygroscopic, powdered samples

Paul W. R. Bessonette and Mary Anne White

Rev. Sci. Instrum. 70, 3113 (1999); http://dx.doi.org/10.1063/1.1149873 (2 pages) | Cited 1 time

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An automated apparatus for dielectric determinations on solid samples was designed to allow cryogenic measurements on air-sensitive, corrosive, hygroscopic, powdered samples, without determination of sample thickness, provided that it is uniform. A three-terminal design enabled measurements that were not affected by errors due to dimensional changes of the sample or the electrodes with changes in temperature. Meaningful dielectric data could be taken over the frequency range from 20 Hz to 1 MHz and the temperature range from 12 to 360 K. Tests with Teflon and with powdered NH4Cl gave results that were accurate within a few percent when compared with literature values. © 1999 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.)
07.68.+m Photography, photographic instruments; xerography
77.22.Gm Dielectric loss and relaxation
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Deconvolution and measurement of bulk and surface optical absorptions in Ti:Al2O3 crystals using photopyroelectric interferometry

Chinhua Wang and Andreas Mandelis

Rev. Sci. Instrum. 70, 3115 (1999); http://dx.doi.org/10.1063/1.1149874 (10 pages) | Cited 1 time

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The extension of our earlier single-layer (monolithic) photopyroelectric (PPE) interferometric theory to include surface and bulk optical absorptions has allowed the measurement of both bulk absorption coefficient and surface absorptance in one single experiment. Based on purely thermal-wave interferometry, the thermal-wave cavity lengths of a PPE interferometer were scanned using pairs of Ti: sapphire crystals with appropriate combinations of figure of merit, surface polish, and thickness. In the conventional single-ended (noninterferometric) PPE technique, the surface reflectivity, surface absorptance, and bulk absorption coefficient are always coupled together. However, PPE destructive interferometry provides a method for extracting highly precise values of one of these optical parameters, without the requirement of equally precise knowledge of the values of the others. © 1999 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
07.20.-n Thermal instruments and apparatus
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Modeling multifrequency eddy current sensor interactions during vertical Bridgman growth of semiconductors

Kumar P. Dharmasena and Haydn N. G. Wadley

Rev. Sci. Instrum. 70, 3125 (1999); http://dx.doi.org/10.1063/1.1149875 (18 pages) | Cited 3 times

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Electromagnetic finite element modeling methods have been used to analyze the responses of two (“absolute” and “differential”) eddy current sensor designs for measuring liquid–solid interface location and curvature during the vertical Bridgman growth of a wide variety of semiconducting materials. The multifrequency impedance changes due to perturbations of the interface’s location and shape are shown to increase as the liquid/solid electrical conductivity ratio increases. Of the materials studied, GaAs is found best suited for eddy current sensing. However, the calculations indicate that even for CdTe with the lowest conductivity ratio studied, the impedance changes are still sufficient to detect the interface’s position and curvature. The optimum frequency for eddy current sensing is found to increase as the material system’s conductivity decreases. The analysis reveals that for a given material system, high frequency measurements are more heavily weighted by the interfacial location while lower frequency data more equally sample the interface curvature and location. This observation suggests a physical basis for potentially measuring both parameters during vertical Bridgman growth. © 1999 American Institute of Physics.
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81.10.Fq Growth from melts; zone melting and refining
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
81.05.Dz II-VI semiconductors
81.05.Ea III-V semiconductors
81.05.Cy Elemental semiconductors
02.70.Dh Finite-element and Galerkin methods

Improvements on a particle feeder for experiments requiring low feed rates

Lin Tang and Wei-Yin Chen

Rev. Sci. Instrum. 70, 3143 (1999); http://dx.doi.org/10.1063/1.1149876 (2 pages) | Cited 8 times

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The center piece of a particle feeder for steady feeding of fine particles at low rates has been modified by sweeping the particles upward into a concentric tube which also serves as the piston support. The new design has demonstrated superior short and long term stabilities of particle feeding rate; moreover, it has significantly extended the operating ranges of the carrier-gas flow rate, particle feeding rate, and particle size and type. © 1999 American Institute of Physics.  
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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)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
47.55.Kf Particle-laden flows
83.50.-v Deformation and flow
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