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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2168-2172 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ge nanocrystal growth in amorphous silicon oxide film was studied using the transmission electron microscopy and x-ray photoelectron spectroscopy techniques. The as-sputtered sample contained mainly GeO2 and Ge suboxides. GeO2 and/or suboxides dissociate when rapid thermal annealed and provide Ge for nanocrystal formation. Nanocrystals of similar size (∼60 Å in diameter) were obtained when annealed at 800 °C. Nanocrystals with diameters of 200–280 Å consisting of multiple twin structures near the Si–SiO2 interface were observed when annealed at 1000 °C. The twin structure was attributed to the enhanced diffusion of Ge at 1000 °C and the short annealing time. Our photoluminescence (PL) results show that the best PL response was obtained with samples that exhibit uniform nanocrystal size. © 2001 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 86 (1999), S. 1398-1403 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman characterization of germanium (Ge) nanocrystals embedded in amorphous silicon oxide (a-SiO2) films synthesized by rapid thermal annealing (RTA) has been carried out. The samples were prepared by cosputtering Ge and SiO2 targets using a rf magnetron sputtering machine. Ge nanocrystals can only be obtained from samples sputtered with six pieces of Ge attached to the SiO2 target. For samples annealed at different RTA temperatures, the Raman spectra indicated a transition from amorphous to nanocrystalline Ge when annealed between 600 and 750 °C. The spectra were analyzed in terms of phonon confinement model and the estimated nanocrystal size was between 20 and 66 Å. A minimum annealing time of 160 s at 750 °C was necessary for Ge nanocrystal formation. Strong visible broadband photoluminescence was observed from the nanocrystals and the photoluminescence showed a blueshift with decrease in the nanocrystal size. The effect of compressive stress on nanocrystal growth was examined by varying the rampup and rampdown rates of the RTA process. The compressive stress was shown to affect the growth of the nanocrystals. © 1999 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3669-3672 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have prepared films of polymethyl methacrylate in which fullerenes (a mixture of C60 and C70) are uniformly embedded. By performing both degenerate four-wave mixing experiments and irradiance-dependent transmission measurements with nanosecond laser pulses of 608-nm wavelength, the third-order nonlinear optical susceptibility of these films is determined to be of the order of 10−10 esu. This susceptibility is dominated by its imaginary part. Excited-state absorption is the main mechanism responsible for the observed nonlinear susceptibility.
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  • 4
    Publication Date: 2015-01-22
    Description: Ta 2 O 5 /TaO x heterostructure has become a leading oxide layer in memory cells and/or a bidirectional selector for resistive random access memory (RRAM). Although atomic layer deposition (ALD) was found to be uniquely suitable for depositing uniform and conformal films on complex topographies, it is hard to use ALD to grow suboxide TaO x layer. In this study, tantalum oxide films with a composition of Ta 2 O 5 were grown by ALD. Using Ar + ion irradiation, the suboxide was formed in the top layer of Ta 2 O 5 films by observing the Ta core level shift toward lower binding energy with angle-resolved X-ray photoelectron spectroscopy. By controlling the energy and irradiation time of an Ar + ion beam, Ta 2 O 5 /TaO x heterostructure can be reliably produced on ALD films, which provides a way to fabricate the critical switching layers of RRAM.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 5
    Publication Date: 2014-10-17
    Description: Influence of post-deposition annealing on interfacial properties related to the formation/annihilation of interfacial GaO x layer of ZrO 2 grown by atomic layer deposition (ALD) on GaN is studied. ZrO 2 films were annealed in N 2 atmospheres in temperature range of 300 °C to 700 °C and analyzed by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that Ga-O bond to Ga-N bond area ratio decreases in the samples annealed at temperatures lower than 500 °C, which could be attributed to the thinning of GaO x layer associated with low surface defect states due to “clean up” effect of ALD-ZrO 2 on GaN. However, further increase in annealing temperature results in deterioration of interface quality, which is evidenced by increase in Ga-O bond to Ga-N bond area ratio and the reduction of Ga-N binding energy.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 6
    Publication Date: 2016-11-10
    Description: A method to measure the contact angle, which is indicative of wetting, using small liquid volumes dispensed directly on microplate wells is described and demonstrated. Experiments with enhanced green protein samples of volumes 4.4–6 μ l showed no measured variance in the contact angle. Experiments with phosphate buffer solution with varied concentrations of a non-ionic detergent (Tween 20) dissolved, however, revealed smaller contact angles with increased detergent concentration. It is experimentally shown that drops can be located up to 7° from the lowest position of the well without affecting the accuracy of contact angle measurements. Numerical simulations confirm the ability of the drops to manifest the correct contact angle despite the lack of axis-symmetry in their shape while residing on a circular surface. This method offers a convenient means to determine the wetting characteristics of different liquid samples in different microplates.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 7
    Publication Date: 2015-03-07
    Description: The effect of post-deposition annealing on chemical bonding states at interface between Al 0.5 Ga 0.5 N and ZrO 2 grown by atomic layer deposition (ALD) is studied by angle-resolved x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that both of Al-O/Al 2 p and Ga-O/Ga 3 d area ratio decrease at annealing temperatures lower than 500 °C, which could be attributed to “clean up” effect of ALD-ZrO 2 on AlGaN. Compared to Ga spectra, a much larger decrease in Al-O/Al 2 p ratio at a smaller take-off angle θ is observed, which indicates higher effectiveness of the passivation of Al-O bond than Ga-O bond through “clean up” effect near the interface. However, degradation of ZrO 2 /AlGaN interface quality due to re-oxidation at higher annealing temperature (〉500 °C) is also found. The XPS spectra clearly reveal that Al atoms at ZrO 2 /AlGaN interface are easier to get oxidized as compared with Ga atoms.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The grazing incidence x-ray reflectivity is a nondestructive and sensitive technique for probing the depth profile of electron density in layered structures. This method has been utilized in the soft x-ray regime to determine the roughness of interfaces, and the epilayer thickness in InxGa1−xAs/InP and InxGa1−xAs/GaAs heterostructures, for x=0.57 and x=0.60, grown by molecular beam epitaxy. By fitting the experimental results to our model, assuming uncorrelated interfacial roughness, we conclude that the top surface roughness does not depend on the type of the substrate or presence of stress in the epilayer, and is always smaller than interfacial roughness. The main factors which control the interfacial roughness are the quality of substrate and/or growth conditions rather than strain or lattice mismatch.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 137-145 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-dimensional fluid model is developed to study the equilibrium flow of electrons in the vacuum gap between the cathode and the plasma of a plasma opening switch. The dynamics of electron flow in the vacuum gap region is illustrated by the distributions of the magnetic field, the electrostatic potential, and the electron density. The dependencies of the switch current and its interruption in the vacuum gap on the dimensions of the vacuum gap, the load impedance, and the electrostatic potential across the gap are investigated. The two-dimensional aspect of the electron flow in the vacuum gap and its effects on the performance of a plasma opening switch are emphasized.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metalorganic chemical vapor deposition (MOCVD) has the potential of emerging as a viable technique to fabricate ribbons, tapes, coated wires, and the deposition of films of high-temperature superconductors, and related materials. As a reduced thermal budget processing technique, rapid isothermal processing (RIP) based on incoherent radiation as the source of energy can be usefully coupled to conventional MOCVD. In this paper we report on the deposition and characterization of high quality superconducting thin films of Y-Ba-Cu-O (YBCO) on yttrium stabilized zirconia substrates by RIP assisted MOCVD. Using O2 gas as the source of oxygen, YBCO films deposited initially at 600 °C for 1 min and at 745 °C for 25 min followed by deposition at 780 °C for 45 s are primarily c-axis oriented and zero resistance is observed at 89–90 K. The zero magnetic field current density at 53 and 77 K are 1.2×106 and 3×105 A/cm2, respectively. By using a mixture of N2O and O2 as the oxygen source substrate temperature was further reduced in the deposition of YBCO films. The films deposited initially at 600 °C for 1 min and than at 720 °C for 30 min are c-axis oriented and with zero resistance being observed at 91 K. The zero magnetic field current densities at 53 and 77 K are 3.4×106 and 1.2×106 A/cm2, respectively. To the best of our knowledge this is the highest value of critical current density, Jc for films deposited by MOCVD at a substrate temperature as low as 720 °C. It is envisioned that high energy photons from the incoherent light source and the use of a mixture of N2O and O2 as the oxygen source, assist chemical reactions and lower overall thermal budget for processing of these films.
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