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  • 1
    Electronic Resource
    Electronic Resource
    Low-temperature photochromic response of gallium-doped bismuth germanium oxide (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3974-3978 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gallium is one of several dopants that electronically compensate the deep donor responsible for the yellow coloration observed in bismuth germanium oxide (BGO). A series of Ga-doped BGO crystals were grown using the Czochralski method to confirm the formation of a trapped hole center following exposure to near band edge light at low temperatures. The deep donor absorption shoulder disappeared for Ga concentrations in the 3%–4% (melt) range. Excitation at 10 K with 3.3 eV light produces photochromic absorption bands. For low gallium concentrations the photochromic bands were the same as the ones observed in undoped BGO. For concentrations of 4% or more the photoinduced absorption consisted of overlapping bands at 1.1, 1.55, and 2.45 eV. These bands grew uniformly with exposure time and annealed together in the 100–120 K temperature range. By comparison with earlier results on Al-doped BGO and bismuth silicon oxide (BSO), we believe that the 1.1 eV band in BGO:Ga and the 1.0 eV band in BGO:Al (and BSO:Al) are due to trapped hole centers ([GaO4]0 and [AlO4]0, respectively).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352862
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  • 2
    Electronic Resource
    Electronic Resource
    The low-temperature photochromic response of bismuth silicon oxide (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1443-1448 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Exposing the photorefractive material bismuth silicon oxide (BSO) at low temperatures to 2.4–3.3 eV light produces photochromic absorption bands. In undoped and Fe-doped BSO these bands appear to consist of a series of overlapping bands ranging from around 1.5 eV in the infrared to near the band edge. The infrared component is always weaker than the visible range contributions. The infrared portion anneals just above 100 K; in some samples this anneal is accompanied by the appearance of additional structure in the visible region. In undoped BSO the major anneal of the photochromic bands takes place above 200 K. If iron is present the photochromic bands are weaker and an anneal stage in the 120–150 K range appears. Bleaching with either 1.51 or 2.28 eV laser light uniformly lowered the photochromic bands in both undoped and Fe-doped BSO. In BSO:Al the aluminum electronically compensates the deep donor centers responsible for the yellow coloration observed in undoped crystals. At low temperatures, photoexcitation using near band-edge light produces the same overlapping bands at 1, 1.38, and 2.45 eV that were observed in BGO:Al. These bands anneal together between 80 and 100 K. The [AlO4]0 center which causes the coloration observed in smoky quartz is a plausible model for the photochromic bands in BSO:Al.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353243
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  • 3
    Electronic Resource
    Electronic Resource
    Clear correlations observed between YBa2Cu3O7−δ thin-film properties and GHz microwave resonator performance (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1789-1791 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated and measured 5 GHz microstrip resonators from a series of YBa2Cu3O7−δ thin films grown on LaAlO3(001) substrates by in situ laser ablation. We have studied the correlations between unloaded quality factor and various film properties, such as transition temperature, width of transition, critical current density, narrowness of x-ray rocking curve, sharpness of electron channeling pattern, and most important substrate temperature during growth. We found that in general, higher transition temperature, higher critical current density, sharper transition, sharper channeling pattern, and narrower x-ray rocking curve correlate positively with good microwave performance. The best quality factor exists for a narrow growth temperature window (around 800 °C). We also report the dependence of quality factor on device power for each film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105092
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  • 4
    Electronic Resource
    Electronic Resource
    Lattice recovery of oxygen-implanted YBa2Cu3O7−δ superconductor (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 189-191 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The regrowth of an oxygen-implanted YBa2Cu3O7−δ thin film was studied by Rutherford backscattering, ion channeling, and x-ray diffraction studies. The atomic composition of the thin film was preserved even after a 1 h anneal at 990 °C, reflecting the high chemical stability of the material obtained by the pulsed laser deposition technique. Two distinct activation energies were determined during the regrowth process: 0.42±0.04 eV at lower temperatures, corresponding to epitaxial growth from the interface, and 0.18±0.03 eV at higher temperatures, presumably associated with homogeneous nucleation and reorientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104214
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  • 5
    Electronic Resource
    Electronic Resource
    Surface outgrowth problem in c-axis oriented Y-Ba-Cu-O superconducting thin films (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1557-1559 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The origin of surface outgrowths in c-axis oriented superconducting Y-Ba-Cu-O thin films has been identified. We find that a,b-axis regions nucleate heterogeneously at second phase regions and rapidly grow outward, leading to the formation of lenticular-shaped outgrowths. The second phase has been identified by electron diffraction and high-resolution electron microscopy to be the Y1Ba3Cu2O7−x phase that forms as microscopic platelet-shaped precipitates on the a-b plane. The heterogeneous nucleation of such outgrowths is general and has been observed in both in situ sputtered and laser-deposited films. It is probably related to the ledge growth mechanism of the c-axis oriented Y-Ba-Cu-O thin film and to the precise overall composition of the film and needs to be studied in detail in order to produce films with smooth surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105176
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  • 6
    Electronic Resource
    Electronic Resource
    Electrical and structural properties of shallow p+ junctions formed by dual (Ga/B) ion implantation (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1362-1364 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrashallow p+ junctions formed by dual implanation of Ga and B with low-temperature rapid thermal anneal (RTA) are reported. The electrical and structural properties of the shallow junction were studied by sheet resistance and diode reverse recovery measurements, Rutherford backscattering channeling, and secondary-ion mass spectrometry. A junction of 400 A(ring) depth (full width at half maximum) and an average carrier concentration of 3×1019 cm−3 were realized with RTA at 600 °C. It is shown that there is excess damage in the dual-implanted junctions which affects the minority-carrier lifetime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102515
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  • 7
    Electronic Resource
    Electronic Resource
    a-axis oriented epitaxial YBa2Cu3O7−x-PrBa2Cu3O7−y heterostructures (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2484-2486 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown YBa2Cu3O7−x-PrBa2Cu3O7−y heterostructures with the perovskite a axis normal to the surface of a variety of (001) oriented substrates using the pulsed laser deposition technique. X-ray diffraction studies indicate little or no formation of the traditional c-axis normal orientation usually nucleated on these substrates, while ion channeling, transmission electron microscopy (TEM), and Raman scattering studies reveal a highly ordered crystalline structure similar in quality to that obtained in the best c-axis oriented films. Superconducting transition temperatures, for current transport in the plane of the films, consistently exceed 80 K, but are probably lower than the optimum 92 K transition expected for YBa2Cu3O7−x due to the presence of growth twin boundaries between grains with the c axis oriented along the two substrate directions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104179
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  • 8
    Electronic Resource
    Electronic Resource
    Epitaxial growth of ferroelectric bismuth titanate thin films by pulsed laser deposition (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1505-1507 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial thin films of ferroelectric bismuth titanate Bi4Ti3O12 have been grown by pulsed laser deposition on single-crystal [100] SrTiO3 substrates. Bismuth titanate has a high Curie temperature (675 °C) and saturation polarization values of 4 and 50 μC/cm2 along the c and b axis, respectively. Its a,b lattice parameters allow thin-film growth on substrates such as SrTiO3, LaAlO3, MgO, etc. These single crystalline films exhibit good quality as evidenced by x-ray diffraction, Rutherford backscattering, and transmission electron microscopy. Applications for these films include memory devices and optical displays.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104128
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  • 9
    Electronic Resource
    Electronic Resource
    Differentiation of mite species by using cellulose acetate and equilibrium polyacrylamide gel electrophoresis of isoenzymes (1990)
    Springer
    Experimental and applied acarology 8 (1990), S. 97-104 
    Details
    ISSN: 1572-9702
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The isoenzymes of various species of medically and economically important mites were studied using cellulose acetate and equilibrium polyacrylamide gel electrophoresis. Interspecific differences in isoenzymes were found, which were species-specific. Intraspecific differences in isoenzymes were also found when individual mites were examined. The efficiency of each technique, and their use in various fields of acarology, are discussed. In addition, possible phylogenetic relationships as revealed by these techniques are suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01193384
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  • 10
    Electronic Resource
    Electronic Resource
    Feeding postures of suspension-feeding larval black flies: the conflicting demands of drag and food acquisition (1991)
    Springer
    Oecologia 85 (1991), S. 457-463 
    Details
    ISSN: 1432-1939
    Keywords: Suspension-feeding ; Boundary layers ; Drag ; Conflicting demands ; Larval black flies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We tested whether larval black flies actively control the positioning of their feeding appendages (labral fans), and if so, whether their posture represents a balance between the conflicting demands of drag and feeding. We compared the postures of live larvae with the postures of larvae killed by heat-shock in three different flow regimes in a laboratory experiment; we assumed that the postures of heat-killed larvae approximated a passive response to drag. The average height of the labral fans above the bed declined significantly in faster flows, and was significantly greater in live than dead larvae. There was also a significant interaction effect, since the difference between the fan heights of live and dead larvae was greater in slower flows. Two mechanisms may contribute to this result. Larvae in slower flows have to increase their fan heights more than larvae living in faster flows to achieve comparable increases in velocity and thus particle flux. In addition, muscular strength may limit the feeding postures larvae can assume. The fan heights of live larvae also varied depending on the concentration of food particles: larvae exposed to low food concentrations held their fans higher above the bed than did larvae exposed to high food concentrations in the same flow regime. This change in posture is due neither to an uneven particle concentration in the boundary layer nor to added drag from particles trapped in the labral fans. Collectively, our results indicate that these suspension feeders actively control their feeding posture, and suggest that these varying postures represent a dynamic balance between the conflicting needs of minimizing drag and maximizing feeding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323756
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