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  • American Institute of Physics (AIP)  (11)
  • The International Institute of Anticancer Research (IIAR)  (1)
  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It was reported that La3Co is an interesting superconductor which has a critical temperature Tc of 4.5 K. Pr3Co and Nd3Co are ferromagnetic materials, which have Curie temperatures of 10 and 25 K, respectively. It was claimed that their magnetic structures are associated with the canting moment reflected to the symmetry of their crystal structure. In this paper we present the results of the specific heat measurement in these compounds in the temperature range from 2 to 30 K by a standard adiabatic heat pulse method. Two phase transitions are observed at 8 and 25 K in Nd3Co. One of them at 25 K corresponds to the Curie temperature mentioned above. Another is the transition corresponds to the moment reorientation, which was observed in the thermomagnetic curves and electrical resistivity measurement. This results claim that the moments are canted in this compounds. Magnetic entropy reaches 90% of R ln 2 at 25 K. However, it increases above the Curie temperature because the crystalline electric field effects plays an important role in this compounds. There are two peaks of 10 and 12 K in Pr3Co. The above temperature corresponds the Curie temperature but another was unknown. Thus we performed the specific heat measurement for Pr7Co3, which is very close to the Pr3Co in the phase diagram. We could observe the phase transition at 12 K for Pr7Co3 in the specific heat measurement and electric resistivity measurement. It is clear that the phase transition at 12 K comes from impurity of Pr7Co3 in our Pr3Co compound. We prepare the good quality sample of Pr3Co and try to examine the specific heat measurement. © 1996 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3653-3654 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relaxation phenomena of the amorphous FeZrBiSiB alloy have been investigated by DSC and electrical and magnetic measurements. It is found that there exist two different relaxation stages of the structural relaxation processes. The mechanism of forming these two relaxation stages is analyzed by the idea of short-range localized atomic arranging movement and medium or long-range cooperative atomic arranging movement. We consider that the effect of the annealing treatments on the Curie temperature of the specimens is caused by the additive effect of ferromagnetic and antiferromagnetic exchange interaction.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 825-827 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The acceleration of an electron by a circularly polarized, high-intensity ultrashort laser pulse in vacuum is studied. It appears that the energy of the electron can be accelerated significantly, and the electron moves almost along the propagation direction of the laser pulse. © 1998 American Institute of Physics.
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: B-doped Si1−xGex layers with Ge fractions, determined by Rutherford backscattering spectroscopy, ranging from 0 to 0.28 and B concentrations, from quantitative secondary-ion spectroscopy measurements, between 5×1016 and 4×1019 cm−3 were grown on Si(001) at temperatures Ts=475–575 °C by gas-source molecular beam epitaxy from Si2H6, Ge2H6, and B2H6. Film thicknesses ranged from 200 nm for alloys with x=0.28 to 800 nm with x=0.05 to 1.4 μm for Si. Structural analyses by high-resolution x-ray diffraction and reciprocal lattice mapping combined with transmission electron microscopy showed that all films were fully strained, with measured relaxations of only (approximately-equal-to)4×10−5, and exhibited no evidence of dislocations or other extended defects. The hole conductivity mobility μc,h in these layers increased continuously with increasing Ge concentrations, whereas the Hall mobility decreased yielding a Hall scattering factor that ranged from 0.75 for Si to 0.26 for Si0.72Ge0.28 but was not strongly affected by B concentration. μc,h, with CB=2×1018 cm−3, varied from 110 cm2 V−1 s−1 for Si0.95Ge0.05 to 158 cm2 V−1 s−1 for Si0.72Ge0.28, compared to 86 cm2 V−1 s−1 for Si, in good agreement with Boltzmann transport model calculations accounting for changes in the valence-band structure due to the effects of both alloying and biaxial in-plane compressional strain. © 1996 American Institute of Physics.
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Secondary-ion-mass spectrometry (SIMS) was used to determine the concentration and depth distribution of B incorporated into Ge(001)2×1 films grown on Ge(001) substrates by gas-source molecular-beam epitaxy using Ge2H6 and B2H6. B concentrations CB (3×1016–4×1019 cm−3) were found to increase linearly with increasing flux ratio JB2H6/JGe2H6 (8.2×10−3–1.7) at constant film growth temperature Ts (300–400 °C) and to increase exponentially with 1/Ts at constant JB2H6/JGe2H6 ratio. The difference in the overall activation energies for B and Ge incorporation over this growth temperature range is (approximately-equal-to)0.22 eV while B2H6 reactive sticking probabilities ranged from 8×10−4 at 300 °C to 2×10−5 at 400 °C. SIMS depth profiles from B modulation-doped samples and two-dimensional δ -doped samples grown at Ts〈350 °C were abrupt to within instrumental resolution with no indication of surface segregation. Structural analysis by in situ reflection high-energy electron diffraction combined with postdeposition high-resolution plan-view and cross-sectional transmission electron microscopy showed that all films were high-quality single crystals with no evidence of dislocations or other extended defects. B doping had no measurable affect on Ge deposition rates. © 1995 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 517-521 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-resolved hot-stage transmission optical microscopy is used to characterize the nucleation and growth kinetics of amorphous GeTe thin-film crystallization. This technique provides experimental measurements of the fraction crystallized, the number of crystallites, and the crystallite size as a function of annealing time and temperature. The fraction-crystallized data are modelled using the Johnson–Mehl–Avrami formalism to give an Avrami exponent of 4, consistent with previous measurements via time-resolved reflection/transmission methods. Microstructural measurements provide sufficient data to deconvolute the individual contributions of nucleation and growth to this exponent. This work shows that crystallization of these films proceeds by nucleation at an increasing rate due to transient effects with isotropic two-dimensional growth in the film plane. © 1995 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 5711-5713 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report that dissociative electron attachment (DEA) to HCl is strongly enhanced by adsorption on the surface of H2O ice. The absolute DEA cross section at ∼0 eV for HCl adsorbed on ice is measured to be ∼4.0×10−15 cm2, which is two orders of magnitude higher than in the gas phase. This enhancement is essentially due to electron transfer from precursor states of the solvated electron in ice to an unfilled molecular orbital of HCl followed by its dissociation. This study indicates that electron-induced dissociation may be a significant process leading to HCl dissociation on ice surfaces in polar stratospheric clouds due to ionization by cosmic rays. © 2001 American Institute of Physics.
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  • 8
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Cl− yield produced by dissociative electron attachment of a submonolayer of CF2Cl2 is enhanced by factors of 102 and 104 when CF2Cl2 is coadsorbed with water ice and ammonia ice, respectively, on a surface at ∼25 K. Moreover, the magnitude of Cl− enhancement increases strongly with decreasing CF2Cl2 concentration. This enhancement is attributed to dissociation of CF2Cl2 by capture of electrons self-trapped in polar water or ammonia molecules. This process may be an unrecognized sink for chlorofluorocarbons in the atmosphere. Cl− ions produced may be directly or indirectly converted to Cl atoms, which then destroy ozone. © 1999 American Institute of Physics.
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  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: B-doped Si(001)2×1 films were grown on Si(001) substrates by gas-source molecular beam epitaxy using Si2H6 and B2H6. B concentrations CB (5×1016–5×1019 cm−3) were found to increase linearly with increasing flux ratio JB2H6/JSi2H6 (9.3×10−5–2.5×10−2) at constant film growth temperature Ts (600–950 °C) and to decrease exponentially with 1/Ts at constant JB2H6/JSi2H6 ratio. The B2H6 reactive sticking probability ranged from (approximately-equal-to)6.4×10−4 at Ts=600 °C to 1.4×10−3 at 950 °C. The difference in the overall activation energies for B and Si incorporation at Ts=600–950 °C is (approximately-equal-to)0.34 eV. A comparison of quantitative secondary-ion mass spectrometry (SIMS) and temperature-dependent Hall-effect measurements showed that B was incorporated into substitutional electrically active sites over the entire B concentration range investigated. SIMS B depth profiles from modulation-doped samples were abrupt with no indication of surface segregation to within the instrumental resolution limit and initial δ-doping experiments were carried out. Structural analysis by in situ reflection high-energy electron diffraction combined with post-deposition high-resolution plan-view and cross-sectional transmission electron microscopy showed that all films were high-quality single crystals with no evidence of dislocations or other extended defects. Temperature-dependent (20–300 K) hole carrier mobilities were equal to the best reported bulk Si:B values and in good agreement with theoretical maximum values. © 1995 American Institute of Physics.
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  • 10
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth rates RGe of epitaxial Ge films deposited on Ge(001)2×1 and Si(001)2×1 substrates from Ge2H6 by gas-source molecular beam epitaxy were determined over a wide range of temperatures Ts (300–800 °C) and impingement fluxes JGe2H6(0.1–1×1016 cm−2 s−1). Steady-state RGe(Ts, JGe2H6) curves were well described at both low and high growth temperatures (Ts≤325 °C and Ts(approximately-greater-than)500 °C) using a model based upon dissociative Ge2H6 chemisorption followed by a series of surface decomposition reactions with the rate-limiting step being first-order hydrogen desorption from Ge monohydride for which the activation energy was found to be 1.56 eV. At intermediate temperatures, however, experimental RGe results exhibited a large positive deviation from model predictions due, as demonstrated by temperature programmed desorption measurements and transmission electron microscopy (TEM) observations, to kinetic surface roughening. Extensive (113) faceting resulted in both an increase in the number of active surface sites and higher reactive sticking probabilities. With increased growth temperatures, the facets became more rounded and film surfaces appeared sinusoidal in cross section. The zero-coverage Ge2H6 reactive sticking probability on Ge(001) in the high-temperature flux-limited regime was found to be 0.052, more than two orders of magnitude higher than that for GeH4. In situ reflection high-energy electron diffraction and post-deposition TEM examinations showed that Ge films deposited on Ge(001) at Ts≤325 °C grew in a layer-by-layer mode exhibiting a smooth flat surface. © 1995 American Institute of Physics.
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