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  • 1
    Electronic Resource
    Electronic Resource
    Magnetism of ultrathin films of Fe on Cu(100) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5209-5211 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetism in ultrathin (1–10 ML) Fe films grown on Cu(100) has been studied by spin-polarized secondary electron emission spectroscopy. The variation of the magnetization with temperature and oxygen adsorption was investigated for various film thicknesses. The orientation of the magnetization for films between 5 and 6 ML thick switches reversibly between perpendicular (at low temperature) to in-plane (at high temperature). The switching transition temperature decreases with increasing film thickness, and is accompanied by a loss of long-range order over a range of 20–30 K. The transition is attributed to the temperature dependence of the perpendicular anisotropy. The effect of oxygen adsorption onto films with perpendicular remanence is to first suddenly turn the magnetization into the plane at a critical coverage, and then to kill the magnetization gradually with continued exposure. This indicates that the uniaxial surface anisotropy at the Fe-vacuum interface plays a major role in the magnetization of the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348077
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  • 2
    Electronic Resource
    Electronic Resource
    Temperature dependence of Raman scattering in hexagonal gallium nitride films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3332-3337 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: First-order Raman scattering of hexagonal GaN single crystal films deposited on sapphire substrate by low pressure metal organic chemical vapor deposition is studied between 78 and 870 K. The temperature dependence of the five GaN Raman modes is obtained. Both the linewidth and Raman shift exhibit a quadratic dependence on temperature in our measured temperature range. Excellent agreement was found between the experiment data and calculated results based on a model involving three- and four-phonon coupling. Our results indicate it is necessary to include the contributions of both the thermal expansion and four-phonon terms in the four-phonon anharmonic processes to explain the change of Raman shift and linewidth with temperature. In addition, a decrease in the splitting between the longitudinal optical and transverse optical phonons with increasing temperature was also observed. From these data a weak nonlinear decrease of the transverse effective charge with increasing temperature is derived. The comparison of the transverse effective charge eT* at room temperature was made between experimental data and theoretical calculations by a pseudopotential expression and bond orbital model. Good agreement between theory and experiment is achieved. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372344
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  • 3
    Electronic Resource
    Electronic Resource
    Interface structure and perpendicular magnetic anisotropy in Pt/Co multilayers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3953-3959 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pt/Co multilayers sputter-deposited in Ar and Xe ambients, and periodic multilayers composed of specific combinations of Pt, Pd, and Co layers, were grown to study the effects of energetic backscattered Ar neutrals on the interface structure. The effects were correlated with the magnetic and magneto-optical properties with emphasis on the perpendicular magnetic anisotropy, K⊥. Films were characterized by high-resolution transmission electron microscopy, x-ray diffraction including grazing incidence geometry, and magnetic circular x-ray dichroism techniques as well as by standard magnetic and magneto-optic methods. It is found that the perpendicular magnetic anisotropy is extremely sensitive to the degree of intermixing, sharp interfaces yielding the largest anisotropy. The three to fourfold difference in K⊥ found between Ar and Xe sputtered films can be directly correlated to the magnitude of the orbital moment contribution 〈LZ〉 in the Co. This orbital contribution is found to be strongly sensitive to the interface sharpness in the films. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358577
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  • 4
    Electronic Resource
    Electronic Resource
    Search for a proximity effect induced gap in gold/high Tc junctions (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1332-1334 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used high-resolution photoemission spectroscopy to search for a proximity effect induced superconducting gap in gold overlayers on c-axis single crystals of Bi2Sr2CaCu2O8 and a-axis thin films of YBa2Cu3O7. These two junction types give us a representative sampling of very well characterized near-ideal interfaces (gold/c-axis Bi2Sr2CaCu2O8) and junctions in which the geometry more strongly favors the existence of the proximity effect but the interfacial quality may not be as ideal (gold/a-axis YBa2Cu3O7). In neither of these junction types did we observe any evidence for a proximity effect induced gap, and we place an upper limit of approximately 5 meV on its existence in the junctions that we have studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104301
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic structure of the gold/Bi2Sr2CaCu2O8 and gold/EuBa2Cu3O7−δ interfaces as studied by photoemission spectroscopy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 307-309 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-resolution photoemission has been used to probe the electronic structure of the gold/Bi2Sr2CaCu2O8 and gold/EuBa2Cu3O7−δ interface formed by a low-temperature (20 K) gold evaporation on cleaved high quality single crystals. We find that the metallicity of the EuBa2Cu3O7−δ substrate in the near surface region (∼5 A(ring)) is essentially destroyed by the gold deposition, while the near surface region of Bi2Sr2CaCu2O8 remains metallic. This has potentially wide ranging consequences for the applicability of the different types of superconductors in real devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104219
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic structure of ceramics and thin-film samples of high Tc Bi2Sr2CaCu2O8+δ superconductors: Effects of Ar+ sputtering, O2 exposure, and Rb deposition (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1970-1972 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic structure of bulk, and, for the first time, thin-film samples of the new class of high Tc Bi2Sr2CaCu2O8+δ superconductors, is investigated by photoemission spectroscopy using synchrotron radiation. Ar+ sputtering and Rb deposition result in disrupted Bi O bonds and subsequent change in the valency of Bi, while oxygen adsorption or annealing in oxygen is found to restore the Bi O bonds. The results also show that adsorbates of O2 and/or Rb readily give rise to a number of new oxygen states in the valence band of Bi2Sr2CaCu2O8+δ. The Ar+-sputtered film is found to be more sensitive to adsorbates of O2 and Rb than the scraped bulk sample, as monitored by the Bi 5d core shifts and the oxygen-induced valence-band states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100672
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  • 7
    Electronic Resource
    Electronic Resource
    Surface structure of Bi2Sr2CaCu2O8+δ high-temperature superconductors studied using low-energy electron diffraction (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2563-2565 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface structure of Bi2Sr2CaCu2O8+δ has been studied using low-energy electron diffraction (LEED). Sharp diffraction spots indicative of a well-ordered surface are observed. The LEED patterns unequivocally show that this type of material preferentially cleaves along the a-b planes of the nearly tetragonal unit cell. A superstructure extending along one of the axes in the a-b plane (b) is found to have a periodicity of 27±0.5 A(ring), in good agreement with earlier studies of the three-dimensional crystal structure. We conclude that the superstructure at the surface is nonlocal in character and reflects the long-range superlattice of the bulk along the b axis. Intensity modulations of the diffraction spots oriented along the b axis are also reported and discussed in terms of the cell dimension of the unit cell along the b axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100532
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  • 8
    Electronic Resource
    Electronic Resource
    Spectroscopic evidence of two-dimensional character of the 90 K Bi2(Sr,La,Ca)3Cu2O8 superconductors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1141-1143 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polarization-dependent angle-resolved photoemission experiments in the constant final state mode (absorption measurements) were performed on single crystals of the Bi-based 2212 material using synchrotron radiation in the photon energy range 10–40 eV. Evidence of polarization-dependent transitions due to Bi 5d→6p, Sr 4p→4d, and Ca 3p→3d excitations is observed. The data show that the electronic charge is highly localized to the layers of the crystal structure, thus providing a direct spectroscopic confirmation of the two-dimensional nature of these types of materials. Polarization-sensitive absorption signals at 14–15 eV attributed to Bi 6s→6p transitions show that the density of states (DOS) of the Bi 6pz holes peaks at about 0.7 eV higher energy than the DOS of the Bi 6px,y holes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101889
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  • 9
    Electronic Resource
    Electronic Resource
    Photoemission study of the surface electronic structure of Bi-Ca-Sr-Cu-O superconductors modified by Ne sputtering, Ag deposition, and heat treatment (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 529-531 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoelectron spectroscopy has been utilized to study the effect on the electronic structure of the Bi-Ca-Sr-Cu-O surface of Ne sputtering, deposition of Ag, and annealing in ultrahigh vacuum, aiming at gaining insight into the role of different processing parameters. The results show that all these treatments significantly reduce the valency of Cu in the superconductor, and strongly modify the electronic states in the valence band. In addition, Ne sputtering or annealing in ultrahigh vacuum gives rise to new features in both the O 1s core-level data and in the valence band. We conclude that the electronic structure of the Bi-Ca-Sr-Cu-O surface is very sensitive to different methods of preparation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100626
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  • 10
    Electronic Resource
    Electronic Resource
    Laser-induced direct formation of C54 TiSi2 films with fine grains on c-Si substrates (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1727-1729 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we report on the direct synthesis of C54 TiSi2 films with fine grains by pulsed-laser irradiation from Ti deposited on Si substrates, using a Q-switched Nd:YAG laser. The films were characterized using micro-Raman spectroscopy, high-resolution transmission electron microscopy, and atomic force microscopy. In comparison with the C54 TiSi2 using the conventional rapid thermal annealing (RTA) of 35 nm thick Ti/Si, which has an average grain size of about 110 nm and film thickness of 50 nm, the laser-induced C54 TiSi2 films vary from 13 to about 42 nm in thickness with different laser scanning speed and the grain size is 85 nm on average. The TiSi2/substrate Si interface is smooth on the atomic scale. Our results demonstrate the unique advantages of the laser-induced formation technique and its potential in deep submicron semiconductor technology. We propose that the C54 phase is formed by solid-state diffusion, rather than melting. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124801
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