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  • 1995-1999  (9)
  • 1945-1949
  • 1999  (9)
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  • 1995-1999  (9)
  • 1945-1949
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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic properties of bulk Eu2/3Ca1/3MnO3 (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5387-5389 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic and structural properties of the bulk manganite Eu2/3Ca1/3MnO3 are characterized using Mössbauer spectroscopy, magnetization measurements, x-ray diffraction, and resistivity measurements. Here it is demonstrated that one can investigate the magnetic properties of manganites using Mössbauer spectroscopy by doping with europium at the rare earth site and using rays from Eu151 as a probe. Mössbauer measurements were performed at several temperatures between 15 and 293 K using a 151Eu source. The spectrum at room temperature is a single line demonstrating paramagnetism with an isomer shift of 0.60±0.02 mm/s. Measurements at room temperature show the Eu to be trivalent and single phase with a linewidth of 2.933±0.004 mm/s, which is comparable to that found for the Mössbauer standard EuF3. Measurements below 100 K show a much broader linewidth which at 15 K is more than twice that found at 293 K and is associated with a magnetic phase transition. Magnetization as a function of magnetic field measurements up to 5 T show the system to be paramagnetic at 300 K and ferromagnetic-like at 50 K. Magnetic susceptibility measurements made between 300 and 4.2 K show the sample to be paramagnetic down to 100 K, where it undergoes a magnetic phase transition. Mössbauer, resistivity, and magnetic measurements all indicate a change in the paramagnetic state around 230 K. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369986
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  • 2
    Electronic Resource
    Electronic Resource
    Advances in experimental technique for quantitative two-dimensional dopant profiling by scanning capacitance microscopy (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 158-164 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Several advances have been made toward the achievement of quantitative two-dimensional dopant and carrier profiling. To improve the dielectric and charge properties of the oxide–silicon interface, a method of low temperature heat treatment has been developed which produces an insulating layer with consistent quality and reproducibility. After a standard polishing procedure is applied to cross-sectional samples, the samples are heated to 300 °C for 30 min under ultraviolet illumination. This additional surface treatment dramatically improves dielectric layer uniformity, scanning capacitance microscopy (SCM) signal to noise ratio, and C–V curve flat band offset. Examples of the improvement in the surface quality and comparisons of converted SCM data with secondary ion mass spectrometry (SIMS) data are shown. A SCM tip study has also been performed that indicates significant tip depletion problems can occur. It is shown that doped silicon tips are often depleted by the applied SCM bias voltage causing errors in the SCM measured profile. Worn metal coated and silicided silicon tips also can cause similar problems. When these effects are tested for and eliminated, excellent agreement can be achieved between quantitative SCM profiles and SIMS data over a five-decade range of dopant density using a proper physical model. The impact of the tip size and shape on SCM spatial accuracy is simulated. A flat tip model gives a good agreement with experimental data. It is found that the dc offset used to compensate the C–V curve flat band shift has a consistently opposite sign on p- and n-type substrates. This corresponds to a positive surface on p-type silicon and to a negative surface on n-type silicon. Rectification of the large capacitance probing voltage is considered as a mechanism responsible for the apparent flat band shift of (0.4–1) V measured on the samples after heating under UV irradiation. To explain the larger flat band shift of (1–5) V, tip induced charging of water-related traps is proposed and discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149558
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  • 3
    Electronic Resource
    Electronic Resource
    Intrinsic picosecond response times of Y–Ba–Cu–O superconducting photodetectors (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 853-855 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report our femtosecond time-resolved measurements on the photoresponse of an epitaxial YBa2Cu3O7−x (YBCO) thin-film photodetector, patterned into a microbridge geometry. By varying the current–voltage biasing conditions between the superconducting and resistive (hot spot) states, we observed transients that correspond to the nonequilibrium kinetic-inductance and the nonequilibrium electron-heating response mechanisms, respectively. The two-temperature model and the Rothwarf–Taylor theory have been used to simulate the measured wave forms and to extract the temporal parameters. The electron thermalization time and the electron–phonon energy relaxation time were determined by the electron temperature rise and decay times, which were found to be 0.56 and 1.1 ps, respectively, in the resistive state. We have also measured the ratio between the phonon and electron specific heats to be 38, which corresponds to a phonon–electron scattering time of 42 ps. No phonon-trapping effect (typical for low-temperature superconductors) was observed in YBCO, in the superconducting state, so the quasiparticle lifetime was given by the quasiparticle recombination time, estimated from the Rothwarf–Taylor equations to be below 1 ps. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123388
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  • 4
    Electronic Resource
    Electronic Resource
    TWO-DIMENSIONAL DOPANT PROFILING BY SCANNING CAPACITANCE MICROSCOPY (1999)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 29 (1999), S. 471-504 
    Details
    ISSN: 0084-6600
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The scanning capacitance microscope (SCM) provides a direct method for mapping the dopant distribution in a semiconductor device on a 10 nm scale. This capability is critical for the development, optimization, and understanding of future ULSI processes and devices. The basic elements of the SCM and its application to nanometer scale metal oxide semiconductor (MOS) capacitor measurements are described. Experimental SCM methods are reviewed. Basic measurements show that nanometer scale capacitance-voltage relations are understood. High-quality probe tips and surfaces are critical for obtaining accurate measurements of two-dimensional dopant profiles. Quantitative modeling of SCM measurement is described for converting raw SCM data to dopant density. An inverse modeling method is presented. Direct comparison between secondary ion mass spectroscopy (SIMS) and SCM-measured dopant profiles are made. Quantitative junction measurements and models are discussed and images of small transistors are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.matsci.29.1.471
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  • 5
    Electronic Resource
    Electronic Resource
    Scanning capacitance microscope methodology for quantitative analysis of p-n junctions (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7774-7783 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantification of dopant profiles in two dimensions (2D) for p-n junctions has proven to be a challenging problem. The scanning capacitance microscope (SCM) capability for p-n junction imaging has only been qualitatively demonstrated. No well-established physical model exists yet for the SCM data interpretation near the p-n junction. In this work, the experimental technique and conversion algorithm developed for nonjunction samples are applied to p-n junction quantification. To understand the SCM response in the active p-n junction region, an electrical model of the junction is proposed. Using one-dimensional secondary ion mass spectrometry (SIMS) data, the carrier distribution in the vertical dimension is calculated. The SIMS profile and carrier distribution is then compared with the SCM data converted using a first-order model. It is shown that for a certain class of profiles, the SCM converted dopant profile fits well to the SIMS data in one dimension. Under this condition, it is possible to identify the metallurgical p-n junction position in two dimensions. Examples of 2D metallurgical p-n junction delineation are presented. In addition, the SCM ability to locate the 2D position of the intrinsic point in the p-n junction depletion region is demonstrated. The SCM probe tip size is found to be a major factor limiting the SCM accuracy on shallow profiles. On junctions with shallow profiles, the SCM tip interacts with carriers on both sides of the junction. As a consequence, a decrease in accuracy and spatial resolution is observed using a first-order conversion algorithm. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370584
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  • 6
    Electronic Resource
    Electronic Resource
    The non-destructive determination of REE in fossilized bone using synchrotron radiation induced K-line X-ray microfluorescence analysis (1999)
    Springer
    Fresenius' journal of analytical chemistry 363 (1999), S. 413-420 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The sensitivity and applicability of the synchrotron radiation induced X-ray microfluorescence (μ-SRXRF) spectrometer at the Hamburg synchrotron laboratory Hasylab for the determination of the distribution of trace concentrations of rare-earth elements (REE) in fossilized bone are discussed and critically compared to those of other trace analytical methods such as instrumental neutron activation analysis (INAA) and LAMP-ICPMS (laser ablation microprobe inductively-coupled plasma mass spectrometry). Measurements were carried out on two bone samples from contrasting terrestrial depositional environments at Olduvai Gorge (Tanzania). Results indicate that the microdistribution of the REE in these biological materials is not homogeneous and that the relative abundance of these elements can provide information on the palaeoenvironment during the fossilization process. The heterogeneous distribution of the REE can be determined in a quantitative and completely non-destructive manner provided the concentrations of individual REE are above 10 μg/g.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051212
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  • 7
    Electronic Resource
    Electronic Resource
    Expansion of Liquid 4He Through the Lambda Transition (1999)
    Springer
    Journal of low temperature physics 115 (1999), S. 89-105 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Zurek suggestedNature 317 , 505; 1985) that the Kibble mechanism, through which topological defects such as cosmic strings are believed to have been created in the early Universe, can also result in the formation of topological defects in liquid 4 He, i.e. quantised vortices, during rapid quenches through the superfluid transition. Preliminary experiments (Hendry et al., Nature 368 , 315; 1994) seemed to support this idea in that the quenches produced the predicted high vortex-densities. The present paper describes a new experiment incorporating a redesigned expansion cell that minimises vortex creation arising from conventional hydrodynamic flow. The post-quench line-densities of vorticity produced by the new cell are no more than 10 10 m −2 , a value that is at least two orders of magnitude less than the theoretical prediction. We conclude that most of the vortices detected in the original experiment must have been created through conventional flow processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021898914014
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  • 8
    Electronic Resource
    Electronic Resource
    Release Rate and Leaching of Starch-Encapsulated Atrazine in a Calcareous Soil (1999)
    Springer
    Soil Science Society of America journal 63 (1999), S. 425-432 
    Details
    ISSN: 1435-0661
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: N -ethyl-N′-(1-methyl-ethyl)-1,3,5-triazine-2,4-diamine] on the environment. A two-part study was conducted to evaluate: (i) atrazine release rate as a function of starch granule size, temperature, and water potential; and (ii) to compare the leaching of SE atrazine with the leaching of a commercial formulation in a calcareous soil. Atrazine release-rates from the starch granules were determined as a function of three granule sizes (1.40-0.85, 0.85-0.43, and 〈0.43 mm) at five temperatures (4, 10, 20, 25, and 35°C), and five matric potentials (0, -0.1, -0.5, -1.0, and -1.5 Mpa). Atrazine release-rates from the starch granules increased with decreasing granule size, increasing temperature, and increasing water potential. To evaluate leaching as function of atrazine formulation, each starch-encapsulated granule size, commercial formulation, and control treatment was replicated six times in irrigated soil columns (0.188 m2× 0.25 m). A pulse of bromide (10.7 kg Br- ha-1) and atrazine (1.7 kg ha-1) were coapplied to the soil columns and effluent concentrations monitored. Irrigation evens of 55 mm in 5 h were applied through drip emitters at 10-d intervals for 120 d for a total application of 11.5 pore volumes. Averaged bromide breakthrough curves for each soil column treatment were similar, which indicated that differences in the averaged atrazine mobilities were a result of formulation and not of heterogeneity in the soil matrix. Starch-encapsulated atrazine leaching decreased with increasing granule size; however, all SE formulations were less mobile than the commercial formulation. After 11.5 pore volumes and 120d, 〉:52% of the commercial atrazine had leached through the soil columns, compared with 〈38% for the smallest starch granule size and 11% for the largest granule. Starch-encapsulated formulations may be an effective tool for reducing pesticide leaching in calcareous soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 9
    Electronic Resource
    Electronic Resource
    Measuring Turbidity in a Near-Critical, Liquid–Liquid System: A Precise, Automated Experiment (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 877-887 
    Details
    ISSN: 1572-9567
    Keywords: liquid–liquid equilibria ; critical state ; experimental method ; turbidity ; methanol ; cyclohexane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A ground based (1g) experiment is in progress that measures the turbidity of the density-matched, binary fluid mixture methanol–cyclohexane extremely close to its liquid–liquid critical point. By covering the range of reduced temperatures t ≡ (T−T c)/T c from 10−8 to 10−2, the turbidity measurements should allow the Green–Fisher critical exponent η to be determined. This paper reports measurements showing ±0.1 % precision of the transmitted and reference intensities, and ±4μK temperature control near the critical temperature of 320 K. Preliminary turbidity data show a nonzero η consistent with theoretical predictions. No experiment has precisely determined a value of the critical exponent η, yet its value is significant to theorists in critical phenomena. Relatively simple critical phenomena, as in the liquid–liquid system studied here, serve as model systems for more complex behavior near a critical point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022687219993
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