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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3621-3623 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin Pb films supported by Al film were made by using cold-rolling and ion-beam thinning techniques. The morphological instability of the Pb film under electron-beam irradiation was investigated by means of in situ transmission electron microscopy observations. It has been found that under electron-beam irradiation, Pb films with an incoherent Pb/Al interface spheroidized into Pb particles, but those with a semicoherent Pb/Al interface were stable in morphology. The morphological stability of thin films depends on the microstructure and the thermodynamic property of the interphase boundary. A critical interfacial energy for the spheroidization of thin films was determined based on a thermodynamics analysis. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2021-06-01
    Description: Using 10.1 × 109J/ψ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy $$ sqrt{s} $$ s = 3.097 GeV and collected with the BESIII detector, we present a search for the rare semi-leptonic decay J/ψ → D−e+νe + c.c. No excess of signal above background is observed, and an upper limit on the branching fraction ℬ(J/ψ → D−e+νe + c. c.) 
    Print ISSN: 1126-6708
    Electronic ISSN: 1029-8479
    Topics: Physics
    Published by Springer
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7615-7617 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Porous Si (PS) layers are prepared by stain etching in a HF/NaNO2 solution on both p- and n-type crystal Si substrates, and are characterized by photoluminescence (PL), electron paramagnetic resonance (EPR), and infrared absorption (IR) spectroscopy. The PL spectra under 488 nm laser excitation exhibit a strong peak at 680–720 nm for various samples of different substrate parameters and remain stable upon aging in air or γ irradiation; as-etched (∼20 min in air before measurement) and aged (for up to six months) samples show no detectable EPR signal but the γ-irradiated samples show an isotropic g=2.006 signal of peak-to-peak linewidth of 1.1 mT supporting an amorphous Si structure; the IR spectra show both hydrogen and oxygen related IR modes in the as-etched samples and the former decreases with aging time in air while the latter increases. Comparing our results with those of anodically etched PS samples we conclude that: (1) the PL peak position of the stain PS seems to be unique and stable as compared with that of the anodic PS varying in 620–830 nm; (2) the isotropic EPR signal of the stain PS reflects no crystallinity, in contrast with the anisotropic signal of the anodic PS; and (3) obvious oxidation in the as-etched stain PS is also in contrast with the nonobservation of oxygen-related IR modes in the as-etched anodic PS. We discuss the results in terms of structural properties and PL mechanism of PS.
    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 69 (1991), S. 5571-5573 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In 1967, Holtzberg, Gambino, and McGuire [J. Phys. Chem. Solids 28, 2283 (1967)] observed that intermetallic Gd5Si4 exhibits TC = 336 K. This is remarkable in that the TC of Gd (∼291 K) is increased by chemical union with a nontransition metal, which is rare, if not unique. In the present study, magnetization-temperature behavior of Gd5Si4 and (Gd1−xMx)5Si4 systems with M=La or Y were studied and compared with the Brillouin function (BF) to see if molecular-field theory is obeyed. Demagnetization near TC is much sharper for the alloys than expected from the BF. As examples, at T/TC = 0.9, the BF for Gd5Si4 gives M/M0 = 0.38, whereas the observed values range from 0.99 [for (Gd0.8Y0.2)5Si4] to 0.5 [for (Gd0.6La0.4)5Si4]. The factors responsible for these strong deviations from the BF and the high-TC values of these alloys are as yet unclear. X-ray patterns for yttrium-doped samples with x=0.1–0.5 and La with x=0.05 and 0.1 appear identical to the pattern for Gd5Si4, indicating no structural change. For La substitution of x=0.2 and above, there is a change from orthorhombic to tetragonal structure. All of the compounds show a decrease in Curie temperature and magnetic moment as Gd is decreased, as expected because of the replacement of Gd by a nonmagnetic species.
    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 69 (1991), S. 3440-3446 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion implantation into Nd:YAG has been used to produce waveguides which are capable of supporting laser action. The refractive index profiles have been characterized as a function of ion dose and energy, implant temperature, and subsequent thermal annealing. Transmission losses down to 1.2 dB/cm have been obtained in the optimized waveguides. There is a temperature independent index enhancement of ∼0.15% in the electronic stopping (guiding) region. The nuclear collision damage is temperature dependent, and shows an initial index increase (∼0.3% for dose 1 × 1016 ions/cm2), but a subsequent decrease of up to several percent, which forms an optical barrier, as has been observed in many other crystalline materials. The best mode confinement and attenuation is obtained by utilizing the low dose nuclear index enhancement produced by several equally spaced implants (multiple energy) to give a broad well with Δn∼0.25%. Several unusual features of the profiles are reported and discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1185-1189 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An extra "strange'' mode has been observed in the extraordinary index mode spectrum of certain optical waveguides produced by He+ ion implantation in LiNbO3. This behaves differently to the normal modes contained within the main optical well of the waveguide, for example when observed at varying wavelengths or after surface polishing. The mode has been shown to be a real guided-wave mode, and has been attributed to a subsidiary optical well located beyond the main nuclear damage optical barrier. It is suggested that this well is produced by the radiation-enhanced diffusion of Li+ towards the nuclear damage barrier, and the mechanism is compared with that responsible for the well on the near side of the barrier which causes the previously reported "missing'' modes.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6027-6029 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A number of metal-bonded Sm2Fe17-N magnets have been fabricated. These magnets exhibit iHc = 5.1–17.0 kOe, Br = 6.4–8.4 kG, (BH)max=5.0–10.8 MGOe, Tc = 757 K, and ρ=6.2–6.7 g/cm3. Powder metallurgical techniques have been employed with a mixture of powdered Sm2Fe17-N and Zn, Sn, or In. Heat treatment is carried out in the temperature range of 160–450 °C in a N2 atmosphere at pressures ranging from 0–900 psi. The effects of Zn, Sn, and In contents and heat treatment conditions on the magnetic properties have been studied. Zn as the binder significantly enhances the coercivity iHc from 1.8–2.5 kOe for Zn-free magnets to 5–17 kOe for 9–20-wt. % Zn-containing magnets. The Fe-Zn phase, FeZn4, and/or Fe3Zn7, formed during heat treatment, may play an important role in producing a high coercivity. Sn-bonded magnets exhibit significant coercivity, whereas the In-bonded materials do not. The coercivity behavior is discussed in terms of the chemistry of the system.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4981-4983 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nd2Co7−xFexB3 alloys have been synthesized and studied at temperatures from 4 to 1100 K at fields up to 90 kOe. The structure and magnetic properties vary significantly with changing Fe content. The main phase is observed to be of hexagonal symmetry for x〈3. For x〉4 it is multiphase, the major phase having tetragonal symmetry. The Tc increases from 330 to 885 K when x varies from 0 to 3, then decreases from 885 to 577 K when x increases from 3 to 7. The saturation magnetization is 8μB/fu at 4.2 K, for Nd2Co7B3; it increases with increasing Fe content. The alloys exhibit a conical (0〈x〈3) and an axial (x〉4) magnetocrystalline anisotropy at 295 K. They all exhibit conical magnetic anisotropy at 77 K.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2695-2699 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Second-harmonic generation (SHG) has been successfully performed in ion-implanted planar waveguides in KTiOPO4. The waveguides were formed by helium implantation, and SHG was achieved using type 2 zero order mode phase matching at a wavelength of ∼1.07 μm. The results indicate that the high nonlinearity of the material remains in the guiding region after ion implantation. The conversion efficiency in a typical guide is estimated at ∼25% for ∼1 μJ pulsed excitation. At a lower input power level, the harmonic green output from the waveguide is 20 times higher than that from the bulk for the same amount of fundamental power. This clearly demonstrates the advantage of using waveguides in achieving frequency doubling for integrated optical devices.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 49-52 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical waveguides have been formed by helium-ion implantation in KTaO3. The implantation forms a confinement barrier near the projected range of the ion by decreasing the refractive index as much as 16% for ion doses of 4×1016 ions/cm2. This is the highest refractive-index change yet reported for ion-implanted crystalline planar waveguides. Guiding modes (with moderately low loss) are produced without the need for annealing out of color centers. During annealing studies, the index change reduces during an anneal stage near 400 °C, but waveguiding is maintained even after anneals to 900 °C. Loss measurements indicate a planar-waveguide loss of 〈1 dB/cm after a 400 °C anneal.
    Type of Medium: Electronic Resource
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