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  • Digitale Medien  (128)
  • 2000-2004  (42)
  • 1935-1939  (42)
  • 1910-1914  (38)
  • 1830-1839  (6)
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  • Digitale Medien  (128)
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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1042-1049 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Nominally pure and iron doped, as-grown, and thermally annealed photorefractive barium–calcium–titanate crystals of the congruently melting composition Ba0.23Ca0.77TiO3 (BCT) are investigated by holographic and conventional electrical techniques. Refractive-index changes, two-beam-coupling gains, photoconductivities, dark conductivities, and bulk-photovoltaic current densities are measured. As-grown and oxidized crystals are hole conductive and at usual illumination conditions (light wavelength 514.5 nm, light intensity between 0.1 and 1 W/cm2) all measured properties are excellently described by an one-center charge-transport model. The effective electrooptic coefficient r333 is only about 30 pm/V and thus much smaller than the value obtained from interferometric measurements. Two-beam-coupling gains as high as 7 cm−1 are achieved. Doping with iron increases considerably the effective trap density, and bulk-photovoltaic fields of the order of some kilovolts per centimeter are observed in iron-doped crystals. Typical response times of iron-doped, as-grown, or oxidized crystals are about 0.5 s at 1 W/cm2. Reduction yields electron-conductive BCT. The dark storage time increases from 6 min in the as-grown state to 3 h upon a slight reduction treatment, but decreases for strongly reduced samples. The investigation reveals that BCT will become a very promising alternative to barium–titanate crystals (BaTiO3) for many applications. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 22-24 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The optical properties of lead formate crystals are investigated, especially those affecting the usage for optical second-harmonic generation. The refractive indexes and the optical absorption are measured in the near-ultraviolet, visible, and near-infrared spectral regions. The data show that the material is suitable for the efficient generation of blue light when pumped with near-infrared laser wavelengths. Phase matching conditions for this application of lead formate are determined both experimentally and by a numerical evaluation of the index data. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3167-3173 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have grown Bi12GeO20 and Bi12SiO20 single crystals from melts with different GeO2 and SiO2 contents, respectively, to investigate the influence of an intrinsic defect, the antisite defect (Bi on Ge or Si site), on the light-induced charge transport. The optical absorption and the effective trap density of the crystals increase with decreasing GeO2 and SiO2 content in the melt. Furthermore, a variation of the photoconductivity is observed. Our results can be described by a one-center model with the antisite defect Bi3+/4+ on Ge or Si site as dominant photorefractive center. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 849-854 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Second order nonlinear optical properties of In-doped lithium niobate crystals have been quantitatively studied from the chemical bond viewpoint. The results show that the second order nonlinear optical response of In-doped lithium niobate crystals at 1079 nm decreases remarkably with increasing In concentration in the crystal. This approximately linear composition-property correlation in In-doped lithium niobate crystals is quantitatively expressed in the current work. Furthermore, the different influences of Mg, Zn, and In dopants, respectively, on the nonlinear susceptibility of lithium niobate single crystals are also compared in the present work. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1365-2494
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Three Lolium perenne L. genotypes collected from different natural habitats were tested for the effects of their fungal endophyte Neotyphodium spp. on plant growth and seed yield. Half the clones of the originally infected plants were subjected to fungicide treatment to eradicate the endophytes. In an experiment, the clones were planted separately into pots and were either watered adequately or subjected to drought stress. In the genotype collected from a dry site, the endophyte infection reduced plant growth at an adequate water supply, but increased regrowth under drought. In the genotype from a periodically either flooded or dry site, endophyte infection significantly promoted the development of reproductive tillers and seed production (effects which are associated with adaptation to drought). In contrast, the genotype that originated from a wet site showed higher sensitivity to drought stress when endophyte infection was present. The results suggest that environmental conditions in the original habitat of the plants may influence the symbiotic interaction between plant and fungus, probably through natural selection. However, endophyte-induced increases in root dry weight and root/shoot ratio were recorded for all three genotypes. These features could be beneficial for plant persistence, especially on sites where water is the growth-limiting factor.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Epitaxial SrBi2Ta2O9 (SBT) thin films with well-defined (001), (116), and (103) orientations have been grown by pulsed laser deposition on (001)-, (011)-, and (111)-oriented Nb-doped SrTiO3 substrates. X-ray diffraction pole figure and φ-scan measurements revealed that the three-dimensional epitaxial orientation relation SBT(001)||SrTiO3(001), and SBT[11¯0]||SrTiO3[100] is valid for all cases of SBT thin films on SrTiO3 substrates, irrespective of their orientations. Atomic force microscopy images of the c-axis-oriented SBT revealed polyhedron-shaped grains showing spiral growth around screw dislocations. The terrace steps of the c-axis-oriented SBT films were integral multiples of a quarter of the lattice parameter c of SBT (∼0.6 nm). The grains of (103)-oriented SBT films were arranged in a triple-domain configuration consistent with the symmetry of the SrTiO3(111) substrate. The measured remanent polarization (2Pr) and coercive field (2Ec) of (116)-oriented SBT films were 9.6 μC/cm2 and 168 kV/cm, respectively, for a maximum applied electric field of 320 kV/cm. Higher remanent polarization (2Pr=10.4 μC/cm2) and lower coercive field (2Ec=104 kV/cm) than those of SBT(116) films were observed in (103)-oriented SBT thin films, and (001)-oriented SBT revealed no ferroelectricity along the [001] axis. The dielectric constants of (001)-, (116)-, and (103)-oriented SBT were 133, 155, and 189, respectively. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2825-2829 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Excimer laser ablation was used to deposit epitaxial thin films of Ba2Bi4Ti5O18 having mostly c-axis oriented grains. The ferroelectric layer was deposited on an epitaxial conducting oxide electrode layer of LaNiO3, the electrode layer in turn being grown on an epitaxial buffer layer stack on single crystalline (100)-oriented silicon wafers of 3 in. diameter. X-ray diffraction measurements indicate a strong c-axis orientation of the ferroelectric layer. Scanning electron microscopy and atomic force microscopy were used to observe the microstructure of the films and these revealed the homogenous quality of the film with good uniformity over the wafers. Well-defined, saturated ferroelectric hysteresis loops were observed in the compound with values of 1.3 and 0.6 μC/cm2 as saturation and remnant polarization values, respectively, and a coercive field of 47 kV/cm. The results of I–V measurements and complex impedance spectroscopy measurements are presented and a defect formula is proposed for the compound. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2849-2852 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: K4Ln2(CO3)3F4 (Ln=Pr, Nd, Sm, Eu, Gd) is a special type of frequency doubling compound, whose crystal structure exhibits a scarcity of fluorine ions. This leads to two different coordination polyhedrons in the general position of K(2) atoms: [K(2)O6F(1)2F(2)] and [K(21)O6F(1)2] in a 2/1 ratio. The chemical bonding structures of all constituent atoms of the compound K4Gd2(CO3)3F4 (KGCOF) are comprehensively studied; moreover, the relationship between the chemical bonding structure and the nonlinear optical (NLO) properties is investigated from the chemical bond viewpoint. The theoretical prediction of the NLO tensor coefficient d11 of KGCOF is in agreement with experimental observation. Theoretical analyses show that the nonlinearity of this crystal type mainly originates from K–O bonds. In addition, the correlation between the NLO tensor d11 and the refractive index n0 of KGCOF is discussed. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2922-2924 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Non-c-axis-oriented ferroelectric SrBi2Ta2O9 (SBT) epitaxial thin films with (103) orientation have been grown by pulsed laser deposition on buffered Si(100) substrates. For the buffer layers, a heterostructure consisting of MgO(111)/YSZ(100)/Si(100) was applied to induce the growth of a (111)-oriented SrRuO3 (SRO) bottom electrode. X-ray diffraction θ–2θ and φ scans revealed well-defined orientation relationships, viz. SBT(103)(parallel)SRO(111)(parallel)MgO(111)(parallel)YSZ(100)(parallel)Si(100); SBT[010](parallel)SRO[01¯1](parallel)MgO[01¯1](parallel)YSZ〈001〉(parallel)Si〈001〉. The ferroelectric measurements of the (103)-oriented SBT films showed a remanent polarization (Pr) of 5.2 μC/cm2 and a coercive field (Ec) of 76 kV/cm for a maximum applied electric field of 440 kV/cm. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3260-3262 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have grown non-c-oriented SrBi2Ta2O9 (SBT) epitaxial thin films with well-defined (116) orientation by pulsed laser deposition on yttria-stabilized zirconia-buffered (YSZ-buffered) Si(100) substrates covered with electrically conductive (110)-oriented SrRuO3 (SRO) bottom electrodes. The epitaxial growth of (110)-oriented SRO films on (100)-oriented YSZ on Si(100) was confirmed both by x-ray pole figures and transmission electron microscopy (TEM) analyses showing a diagonal-type rectangle-on-cube epitaxy of SRO on YSZ with respect to the substrate and yielding specific multiple twins which originate from the particular in-plane positioning of SRO on YSZ. Cross-sectional TEM analyses revealed a roof-like morphology at the SBT/SRO interface while the other interfaces are sharp. The ferroelectric measurements of the (116)-oriented SBT films show a remanent polarization (2Pr) of 6.8 μC/cm2 and a coercive field (2Ec) of 142 kV/cm for a maximum applied electric field of 283 kV/cm. A comparable hysteresis loop recorded from local piezoresponse by an atomic force microscope working in a piezoelectric mode has also been obtained. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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