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  • 1
    Electronic Resource
    Electronic Resource
    Structure and crystallization of low-pressure chemical vapor deposited silicon films using Si2H6 gas (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5427-5432 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microstructures of silicon films deposited on SiO2 substrates by low-pressure chemical vapor deposition using Si2H6 gas were investigated and compared to those using conventional SiH4 gas by transmission electron microscopy and x-ray diffraction. The deposition rate of the Si2H6 process was about ten times higher than that of SiH4 process at low temperatures (〈550 °C). The transition deposition temperature from amorphous to polycrystalline film was found to be around 580 °C, which was similar to that of the SiH4 process. The film deposited at 600 °C was partially crystalline and had equi-axed grains with the largest average grain size of 0.3 μm while the films using SiH4 has needle-like columnar grains with smaller sizes (200 A(ring)). The x-ray diffraction analysis showed that the structural disorder to amorphously deposited Si films increases as deposition temperature decreases. The grain size in the film after crystallization at 600 °C strongly depended on the deposition temperature and the deposition rate, producing a larger grain size at a lower deposition temperature and/or at a higher deposition rate (Si2H6 deposition compared to SiH4 deposition). The apparent increase in grain size can be explained as a result of the lowered number of crystal nuclei due to a decrease in the number of pre-existing microcrystallites serving as heterogeneous nucleation seeds. When the deposition rate was lower than the critical value (approximately 2–4 nm/min), the grain size in the crystallized film decreased for both SiH4 and Si2H6 films. The maximum grain sizes were 4.5 and 0.3 μm at the deposition temperatures of 485 and 550 °C for the films using Si2H6 and SiH4 gases, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350565
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  • 2
    Electronic Resource
    Electronic Resource
    Computer simulation of Si-implanted GaAs (001) single crystals (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 229-233 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A computer simulation based on the binary collision approximation has been performed to investigate the Si implantation efficiency, the Si depth profile, and the vacancy formation for Si-implanted GaAs (001) crystals. The results reveal a strong dependence on the incident angle of the Si source. The calculated depth profile of Si agrees well with the experimental results from secondary-ion mass spectroscopy. The simulated distribution of vacancies is shallower than that of Si atoms. Also, the calculated number of Ga vacancies exceeds that of As vacancies, which suggests that the Si atoms easily occupy the Ga sites and are activated as donors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352164
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  • 3
    Electronic Resource
    Electronic Resource
    Low-energy conversion electron Mössbauer spectroscopy using a chevron microchannel plate detector (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2570-2573 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A detection system for conversion electron Mössbauer spectroscopy is described. A chevron microchannel plate assembly attached to a two-stage electrostatic lens is used to preferentially detect electrons with energies ≤15 eV. Mössbauer spectra collected with these electrons can provide information about a variety of solid-state surface phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143869
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  • 4
    Electronic Resource
    Electronic Resource
    Absolute measurement of spatial and spectral characteristics of bremsstrahlung using the photoexcitation of nuclear isomers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2298-2305 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method of obtaining absolute, direct measurements of the spatial and spectral characteristics of bremsstrahlung is discussed. This technique, called x-ray activation of nuclei (XAN) is based on the use of well-known photonuclear reactions which populate long-lived nuclear isomers. These populations sample incident photon continua at discrete excitation energies and effectively store this information for convenient retrieval following the irradiation of gram-sized targets. Recently a series of experiments has been conducted which has significantly expanded the available data for the photoexcitation of a wide range of isomers at higher energies. Thus it has become feasible to extend the use of XAN to energies approaching 4 MeV. The utility of this technique is demonstrated by the characterization of bremsstrahlung from the newly installed research linac at the University of Texas at Dallas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143925
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  • 5
    Electronic Resource
    Electronic Resource
    Diminution of the surface states on GaAs by a sulfur treatment (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1959-1961 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface chemical properties of a GaAs layer grown by molecular beam epitaxy were investigated by photoluminescence (PL) and photoreflectance (PR) measurements. While the intensity of the PL spectra for the sulfur-treated GaAs, using a (NH4)2Sx solution, increased 75 times compared to that for the as-grown GaAs, the peaks for the as-grown GaAs measured by PR vanished after a sulfur treatment. These results indicate that the surface state acting as the nonradiative recombination centers was passivated by the sulfur. The chemical adsorption behavior resulting from the sulfur is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357656
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  • 6
    Electronic Resource
    Electronic Resource
    Current controlled GaAs/AlGaAs multiple quantum well phase shifter operating at 0.9 μm (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2363-2365 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An optical phase shifter with current injection has been demonstrated in a GaAs/AlGaAs multiple quantum well (MQW) single mode waveguide. Phase shifts at different wavelengths have been measured and compared with the theory in L. Banyai and S. W. Koch, Z. Physik B 63, 283 (1986). A 3π phase shift has been achieved in a 400-μm-long waveguide with almost no material absorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106016
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  • 7
    Electronic Resource
    Electronic Resource
    Laterally injected low-threshold lasers by impurity-induced disordering (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3375-3377 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Novel laterally injected lasers were fabricated by impurity-induced disordering (IID). The laterally injected IID (LID) lasers have a self-aligned structure and planar configuration; its processing procedures are almost identical to that used for our recently reported vertically injected IID lasers, and are considerably simpler than those of any other laterally injected laser yet reported. The LID lasers have a minimum threshold current Ith=3.2 mA (typical Ith=4 mA) and a maximum light output 11 mW, with a differential quantum efficiency ηd=32% per facet under room-temperature continuous-wave operation. The LID lasers can also be injected vertically by deliberately using an n+-doped (instead of semi-insulating) GaAs substrate and making additional ohmic contacts on the bottom surface of the wafer. A number of interesting aspects about the LID lasers were revealed by comparing the L-I characteristics of the laser under different injection modes, and by studying the I-V characteristics of different combinations of the top and bottom ohmic contacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105679
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  • 8
    Electronic Resource
    Electronic Resource
    Mössbauer effect measurement of the recoil-free fraction for 57Fe implanted in a nanophase diamond film (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1221-1223 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Mössbauer effect was used to investigate films of nanophase diamond (NPD) implanted with isotopically pure 57Fe at a dose of 5×1016 atoms/cm2 and an energy of 20 keV. When defects and voids created by the implantation were repaired with an overcoating layer of NPD, the recoil-free fraction at room temperature for these samples was found to be fdia=0.94±0.06 with a corresponding Debye temperature of 1140 K. This relatively high value for f makes NPD films a promising host matrix for microgram quantities of Mössbauer isotopes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110845
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  • 9
    Electronic Resource
    Electronic Resource
    Measurement of Residence Time Distribution of Fluid and Particles in Turbulent Flow (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 56 (1991), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Residence time distribution (RTD) of fluid and particles was measured in the holding tube of an aseptic processing system. A unique injector device instantaneously injected a large number of particles at one time without interruption of flow. A fraction collector device sampled exiting fluid at 1-sec intervals. Exiting particles at specific lapsed times from injection, were counted from those collected. RTD of fluid was determined by dye injection. RTD of fluid and particles under turbulent flow fitted a normal distribution function. Mean residence time of fluid was 0.975 times that calculated from volumetric flow rate with standard deviation ± 4.16%. Mean residence time of particles was 1.032 times that of the fluid, standard deviation was ± 4.62%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1991.tb08024.x
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  • 10
    Electronic Resource
    Electronic Resource
    Mono-ortho- and non-ortho-substituted polychlorinated biphenyls in human milk from Mohawk and control women: Effects of maternal factors and previous lactation (1994)
    Springer
    Archives of environmental contamination and toxicology 27 (1994), S. 431-437 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Fifty-four individual human milk samples from 50 mothers (20 Mohawks and 30 controls) were analyzed for four non-ortho- and eight mono-ortho-substituted polychlorinated biphenyls (PCBs). Mean total coplanar PCBs concentrations were 49 ng/g and 55 ng/g lipid for Mohawk and control women, respectively. A statistical evaluation of all analytical data reveals no significant difference of total coplanar PCB level between Mohawk and control women. The level of these contaminants is influenced by the age of the mother, number of breastfed children, and length of nursing period. Older women, primiparae, and cigarette smokers had higher levels of coplanar PCBs. In general, women had higher levels of coplanar PCBs in the first lactation and in the earlier samples of a given lactation, while levels declined both with duration of breast-feeding and with number of children nursed. The contribution of individual non-ortho- and mono-ortho-substituted PCB congeners to the total calculated toxic equivalent values (ΣTEQ) was assessed for the breast milk samples. The levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in human milk of pooled specimens from Los Angeles, California and Binghamton, New York, widely separate cities in the United States (Schecter et al. 1989), were presented for reference purpose. The main contributions to the ΣTEQ were PCB congeners #118 (25.8 pg/g lipid), #126 (25 pg/g lipid), #105 (10.8 pg/g lipid), and #156 (7.4 pg/g lipid). Collectively, these compounds accounted for 70% of the ΣTEQ values. Based on the TEFs proposed by Safe (1990), the overall TEQs calculated for the monitored PCBs, were about five times those due to total PCDD/Fs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213183
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