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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 773-782 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability of luminance-voltage characteristics (L-V) has been investigated on ZnS:Mn electroluminescent films grown by chemical vapor deposition. It is found that the aging pattern varies between the positive shift (P shift) and the negative shift (N shift) with the growth temperature. In both cases the L-V curve, the current-voltage relationship, and the symmetry of the light emission with respect to the voltage polarity are strictly cooperative during the aging process. The N shift appears to be dominant when the current is limited by electron injection from the interface, whereas the P shift becomes dominant under the bulk limited conduction, accompanying an excellent symmetry of the emission. A high-field-conduction characteristic in the ZnS layer, which is a decisive factor to determine the aging pattern, is significantly affected by its stoichiometry, grain size, and impurity content. It has been further clarified that the N shift consists of the combination of a softening and a shifting in the L-V relation, which are defined as the effect due to the asymmetric polarization and the band bending in the ZnS layer, respectively. This study demonstrates a stable L-V characteristic without shifting the threshold voltage. The difference between the P shift and the N shift is discussed on the basis of the crystalline property and the carrier transport mechanism.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1522-1524 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stacking faults of cubic SiC films grown on Si (100) were investigated by the electrolytic etching. We find an exponential reduction of the defect density with an increase of film thickness and the anisotropy in the density for the films on off-axis Si (100) substrates. The defect reduction along the offset direction 〈011〉 is explained from the atomic step effect limiting the length of stacking faults to smaller than the equilibrium value. In addition, the defects are eliminated by controlling the film thickness and the size of the growth area using patterned substrates. Since the defects in SiC are metastable, the film thickness required for defect-free crystal is larger than (square root of)2× the lateral dimension.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3028-3034 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relative amount of fluorine(F) to terbium(Tb), F/Tb, in a ZnS:Tb,F electroluminescent film deposited by rf-sputtering method sensitively varies with Tb concentration and preparation conditions. Values of F/Tb are about 1 for the films with low Tb concentrations below 0.5 at. % or the films annealed at 600 °C. The presence of a TbF3 molecular center is inconceivable except for the nonannealed films with relatively high Tb concentrations. It was clarified that variations of the emission spectra and the decay rate with Tb concentration are attributed to the change of F/Tb in the ZnS film. Furthermore, the surprising result is that the Tb-F center has the better emission efficiency, rather than the TbF3 center. A brightness exceeding 600 ft L was obtained under 1-kHz pulse excitation by adjusting the concentration ratio F/Tb to about 1. The real nature of the Tb-F center as well as the role of F− ions are discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1657-1659 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si1−xCx (x∼0.5) films have been prepared by glow discharge decomposition of SiH4, CH4, and H2 gas mixtures. Their structural properties are examined by infrared absorption and reflection electron diffraction. It is found that the film structure depends on the ratio of source gas to hydrogen gas [(SiH4+CH4)/H2], and microcrystalline films can be obtained even at a low temperature of 350 °C when the source gas ratio is less than 0.004.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3650-3657 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The excitation spectrum for terbium (Tb) emission in a ZnS:Tb,F film varies sensitively with Tb concentration, the amount of fluorine (F) relative to Tb, post-deposition annealing, and the temperature of measurement. There are at least three kinds of channels for the excitation of Tb3+ ions; namely, resonant energy transfer from the recombination of an electron-hole pair, direct transitions between the 4f 8 configuration states of a Tb3+ ion, and the indirect excitation via lattice defects. A rapid quenching of photoluminescence (PL) is observed above 0.2 at. % of the Tb concentration in the case of indirect excitation of energy transfer. The PL intensity additionally reduced in the presence of F− ions, even at the same Tb concentration. In contrast, when the Tb3+ ions are directly excited to the 5D3 energy state, the PL intensity increases proportionally up to a maximum of about 2 at. %. The luminance of the electroluminescent device behaves in the same way. Another excitation band is found in an energy region slightly below the band gap of ZnS, and is identified as due to Tb-related complexes associated with sulfur interstitials. The PL characteristics obtained with three excitation channels are also compared with the electroluminescence (EL) characteristics, concerning the effects of post-deposition annealing and measurement temperature. The excitation mechanism of electroluminescence can be explained on the basis of the direct impact model, and the real nature of the energy transfer process is also discussed.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature dependencies of Hall mobility of nondoped and nitrogen-doped n-type β-SiC films have been analyzed using a conventional theoretical model. Considering acoustic, polar optical, and piezoelectric lattice scatterings, as well as ionized and neutral impurity scatterings, theoretical calculations well fitted to the experimental results are obtained at 70–1000 K. Contributions of acoustic, polar optical, and piezoelectric scatterings to the whole lattice scattering are 84%, 14%, and 2% at 300 K, respectively. Impurity compensation ratio NA/ND of nondoped films increases from 0.45 to 0.96 with increasing Si/C ratio in the source gases. Nitrogen-doped films show constant compensation ratios of 0.25–0.30 with various doping amounts. These values are different from the previous results obtained by the analysis of temperature dependencies of carrier concentration.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Schottky barrier contacts have been made on β-SiC single crystals grown by chemical vapor deposition on Si substrates, and their capacitance-voltage and current-voltage characteristics are measured. Dependence of the Schottky characteristics on Si substrate orientation [(n11), n=6, 5, 4, 3, 1, and (100)] is examined. The current-voltage characteristics of the Schottky diodes of the β-SiC films on Si(611) and Si(411) are excellent compared with the conventional Schottky diodes on Si(100). The barrier height is determined by the pulsed capacitance-voltage method. Capacitance-voltage characteristics are measured by this method avoiding the effects of deep levels which are not ionized at room temperature. The dependence on the Schottky metal (Pt and Au) is examined. Both Pt-Schottky diodes and Au-Schottky diodes show good rectification characteristics. The barrier height of the Pt-Schottky diodes is 1.3–1.8 eV and that of the Au-Schottky diodes 1.0–1.6 eV, depending on the substrate orientation. For the same substrate orientation the barrier height for Pt is found to be 0.1–0.3 eV larger than that for Au.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1435-5604
    Keywords: Key words: competitive RT-PCR ; vitamin D receptor ; polymorphism ; bone mineral density ; messenger RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: The association between polymorphisms in the vitamin D receptor (VDR) gene and bone mineral density (BMD) has been studied by many investigators. However, the question of how polymorphisms in the gene modulate the function of the VDR remains to be answered. To address this issue, we examined the mRNA levels of the VDR in relation to polymorphisms. First, we compared the levels of mRNA between the allele with the polymorphic TaqI-digestive site (t) and nondigestive site (T) located at exon 9 of the VDR gene determined by reverse transcription-polymerase chain reaction (RT-PCR). Total RNA was extracted from peripheral mononuclear cells in volunteers whose genotype is Tt. After the amplification of cDNA by PCR, the amplified fragments were digested by TaqI. The digested (t) and undigested (T) fragments were visualized by ethidium bromide and semiquantified by an image analyzer. In 24 subjects, the mRNA levels of allele t were significantly higher than those of allele T (1.35 fold, P 〈 0.001). Second, the VDR mRNA levels were estimated by competitive RT-PCR in 60 healthy subjects (35 TT, 24 Tt, 1 tt). The competitive template was 47 bases shorter than the product of the wild-type gene. After RT-PCR, the mRNA level was determined by a comparison with the competitive fragments. No significant difference in the mRNA level was observed between two groups (1.75 ± 0.84 and 1.65 ± 0.99 10−13 mol/g total RNA in TT and Tt, respectively). In addition, no significant relationship was observed between the VDR mRNA levels and BMD in the 23 subjects whose BMD data were available. In conclusion, higher mRNA levels of allele t than T were detected, but the difference did not result in higher levels of VDR mRNA in subjects with the Tt genotype compared to those with the TT genotype.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1435-232X
    Keywords: Key words Fanconi-Bickel syndrome ; Glycogen storage disease type XI ; Glucose transporter 2 ; Nonsense mutation ; Japanese patient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Fanconi-Bickel syndrome (FBS), or glycogen storage disease type XI, is a rare autosomal recessive disorder characterized by hepatorenal glycogen accumulation, Fanconi nephropathy, and impaired utilization of glucose and galactose. Recently, this disease was elucidated to link mutations in the glucose transporter 2 (GLUT2) gene. Only three mutations in three FBS families have been reported. Therefore, it is important to elucidate mutations in the GLUT2 gene in FBS by answering the question of whether the syndrome is a single gene disease. In this report, we describe two patients in two unrelated families clinically diagnosed with FBS. No mutation in the entire protein coding region of the GLUT2 gene was detected in patient 1, which suggested that no mutation existed in the GLUT 2 gene, or that some mutations had affected the expression of the GLUT 2 gene. In patient 2, a novel homozygous nonsense mutation (W420X, Trp at codon 420 to stop codon) was detected. These results support the correlation between GLTU2 gene mutation and FBS syndrome. However, many patients must be analyzed to determine whether other genes are involved in FBS.
    Type of Medium: Electronic Resource
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