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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4268-4273 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical constants of tetrahedral amorphous carbon (ta-C) films in the infrared region and at a wavelength of 633 nm were investigated. The ta-C films were prepared by the filtered arc deposition technique under different carbon ion energies of 22–320 eV. The ta-C films contained high sp3 bonding of 82%–93% and had very smooth surfaces. The optical band gap was found to be controlled essentially by the presence and arrangement of the sp2 sites in the ta-C films. The real and imaginary parts, ε1 and ε2, of the dielectric constant, refractive index, n, and extinction coefficient, k, of ta-C films were determined from measurements of infrared reflection and spectroscopic ellipsometry. The results indicated that in our region of investigation ta-C films exhibited a fine transparency at a wavelength of 633 nm, especially in the infrared region. Both n and k, and consequently, ε1 and ε2, showed considerable variation in ion energy, and had minimum values approaching those of diamond for film prepared at an ion energy around 220 eV. The dependence of the optical constants on the sp3 content of ta-C films indicated that with increased sp3 content, ta-C film possessed a dielectric constant, refractive index and extinction coefficient much closer to that of diamond. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8098-8102 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A multilayer structure with alternating metal and semiconductor layers is proposed to occur in tetrahedral amorphous carbon (ta-C) films prepared by using an intermittent layer-by-layer deposition method. In this model, the multilayers can be represented as A/B/A/B/.../A/B/A stacks, in which A is considered to be a semimetallic sp2-rich graphite-like layer with B being a semiconducting sp3-rich diamond-like layer. According to the proposed structural model, the electron field emission properties of the ta-C multilayers that could be modulated by adjusting the total number of layers, layer thickness and sp3 content of each layer have been predicted. Correspondingly, three kinds of ta-C multilayers were designed and deposited to confirm this model by enabling us to measure the electron field emission properties. Agreement between the prediction and the experimental results has been observed. It was found that field emission from ta-C multilayers can be optimized by changing the number of layers, layer thickness and sp3 content of each layer. In our experiments, a threshold electric field (Eth) as low as ∼5 V/μm has been obtained for field emission from ta-C multilayers with a total of 20 layers and with a 10 nm layer thickness. © 2000 American Institute of Physics.
    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 87 (2000), S. 2874-2879 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nitrogen incorporated amorphous carbon (a-C:N) films on silicon (111) wafer, quartz, and Ti/C substrates with nitrogen concentration up to 20 at. % are prepared by filtered arc deposition. The nitrogen concentration and area density of the films were measured by Rutherford backscattering. The electrical properties of the films were investigated by Hall electrical measurements. The optical properties of the films were characterized by ultraviolet–visible and infrared reflection spectrometry. Results indicate that the optical band gap and area density of a-C:N films decrease with increasing nitrogen pressure, accompanied with an increase of nitrogen concentration and reflectivity of the films. Furthermore, the influence of nitrogen concentration on the optical band gap of the films is discussed. The dielectric constant, refractive index and absorption coefficient of a-C:N films in infrared region were investigated. The results indicate that the optical constants of a-C:N show considerable variation with wave number and nitrogen content. The variation of optical properties and optical constants of a-C:N films may be due to the development of graphite-like structure with the increasing of nitrogen content in these films. © 2000 American Institute of Physics.
    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 88 (2000), S. 7060-7066 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Carbon nitride thin films were deposited by pulsed laser deposition with nitrogen ion beam assistance at a substrate temperature varying from room temperature to 800 °C. The effect of the substrate temperature on the nitrogen content, surface morphology, structure, and electrical property of the carbon nitride films was investigated. The deposited films were characterized by atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and four-probe resistance. The nitrogen content of the deposited films reached its maximum value of 25% at a substrate temperature of 400 °C. AFM images revealed that an island structure occurred and developed on the surface of the films deposited at the high substrate temperature. FTIR and XPS spectra showed the existence of sp3C–N and sp2C(Double Bond)N bonds in the deposited films. The deposited carbon nitride films had an amorphous structure with two carbon nitride phases inclusions, which had a stoichiometry near C3N4 and a variable stoichiometry from C5N to C2N, respectively. With the increase in substrate temperature, the relative content of the sp3C–N bonds, i.e., the C3N4 phase, increased and the crystallization degree of the deposited films enhanced, which were confirmed by the Raman analysis. Very few C(Triple Bond)N bonds in the films were found as compared to other carbon–nitrogen bonds. Electrical resistivity exhibited the highest value for the film deposited at 400 °C. Investigation results indicated that the high substrate temperature could promote the formation of C3N4 phase. © 2000 American Institute of Physics.
    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 88 (2000), S. 2305-2308 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Visible Raman spectroscopy excited at 532 nm was used to characterize the carbon bonding in tetrahedral amorphous carbon (ta-C) films. The vibrational modes of the sp3 bonding in ta-C films were revealed directly. An additional Raman band occurring below 1350 cm−1 was observed. It consisted of two features centered on ∼1270 and ∼1170 cm−1, which were associated with sp3 bond stretching. The observed sp3 related Raman spectrum approached the vibrational density of states of amorphous diamond. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A metal–ferroelectric–semiconductor (MFS) structure has been developed by depositing SrBi2Ta2O9 (SBT) films directly on n-type (100) Si by pulsed laser deposition. In the MFS structure, evidence for ferroelectric border traps in the SBT film has been obtained by high-frequency capacitance–voltage (C–V) measurement. When the ramp rate of voltage is higher than 200 mV/s, typical ferroelectric C–V hysteresis loops with the counterclockwise direction are obtained in C–V plots. When the ramp rate is lower than 80 mV/s, the ferroelectric hysteresis loops are replaced by the trap-induced ones with the clockwise direction. This pronounced change results from the fact that more and more border traps in SBT can communicate with the underlying Si. The border-trap density at the ramp rate of 10 mV/s is as high as 1.8×1012 cm−2. Moreover, the width of the hysteresis loops changes linearly with the logarithmic decrease in ramp rate, which is consistent with the ferroelectric border traps communicating with Si by tunneling or a thermally activated process. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 444-446 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaN metal–semiconductor–metal photoconductive detectors have been fabricated on Si(111) substrates. The GaN epitaxial layers were grown on Si substrates by means of metalorganic chemical-vapor deposition. These detectors exhibited a sharp cutoff at the wavelength of 363 nm and a high responsivity at a wavelength from 360 to 250 nm. A maximum responsivity of 6.9 A/W was achieved at 357 nm with a 5 V bias. The relationship between the responsivity and the bias voltage was measured. The responsivity saturated when the bias voltage reached 5 V. The response time of 4.8 ms was determined by the measurements of photocurrent versus modulation frequency. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 191-193 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron field emission properties of tetrahedral amorphous carbon films of different thicknesses have been studied. The experimental results indicate that there exists no close relationship between threshold electric field and film thickness. Different field emission models are used to examine the experimental results in order to explain the thickness-independent electron field emission properties. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Allergy 55 (2000), S. 0 
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Allergy 55 (2000), S. 0 
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Profilin (Hev b 8) in natural rubber latex (NRL) has been assumed to be an important allergen. Since latex profilin has a molecular mass similar to two other latex allergens (Hev b 1 and Hev b 6.03) in the 14-kDa range, it is difficult to obtain sufficient amounts of purified native profilin for investigations and diagnostics. The present study aimed to produce recombinant latex profilin (rHev b 8) and study its IgE-binding reactivity. Methods: A profilin-specific cDNA encoding the latex profilin from Hevea brasiliensis leaves was synthesized and subcloned, and the rHev b 8 was overexpressed in fusion with the maltose-binding protein (MBP) in E. coli. The IgE-binding reactivity of rHev b 8 was studied by immunoblotting, immunoblot inhibition experiments, and the Pharmacia CAP method, with 25 sera from health-care workers with latex allergy and 17 sera from latex-sensitive spina bifida patients. Results: rHev b 8 was found to have 131 amino acids and a sequence identity of 75% with birch profilin (Bet v 2). Analysis by the CAP system revealed the presence of rHev b 8-specific IgE antibodies in two out of 17 sera from spina bifida patients and in five out of 25 sera (20%) from health-care workers. Two subjects of the latter group with rHev b 8-specific IgE showed negative results in the skin prick tests with tree-pollen extracts and had no IgE to rBet v 2, indicating the presence of IgE-binding epitopes on the Hev b 8-molecule which do not cross-react with birch profilin. Immunoblot inhibition assays using MBP-rHev b 8 as inhibitor confirmed the presence of latex profilin in the NRL extract. IgE binding to the native latex profilin could be completely inhibited by the MBP-rHev b 8. Conclusions: Latex profilin represents a minor allergen in NRL and may have IgE-binding epitopes different from Bet v 2.
    Type of Medium: Electronic Resource
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