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  • 1
    Electronic Resource
    Electronic Resource
    Epitaxial ZnS films grown on GaAs (001) and (111) by pulsed-laser ablation (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7818-7822 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pulsed KrF (248 nm) laser ablation of a polycrystalline ZnS target has been used to grow very smooth and carbon-free, epitaxial ZnS thin films on GaAs (001) and (111). Films were grown at temperatures of 150–450 °C, using a rotating substrate heater and deposition geometry that produces highly uniform film thickness, without nucleation or surface-roughening problems. X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) show that the ZnS films are fully epitaxial (in-plane aligned). Films grown at the optimum temperature of 325 °C have x-ray rocking curve widths that are indistinguishable from molecular-beam-epitaxy-grown ZnS/GaAs films of the same thickness. Rutherford backscattering spectrometry and HRTEM show that in films ∼275 nm thick, the ∼150 nm nearest the GaAs-ZnS interface is highly faulted, due to the ∼4.1% lattice mismatch and/or the low ZnS stacking fault energy, but the upper ∼125 nm is much less defective. The anisotropy of the ZnS epitaxial growth rate between the GaAs (001) and GaAs (111) surfaces was found to be slightly temperature dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353956
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  • 2
    Electronic Resource
    Electronic Resource
    Y-Ba-Cu-O thin films grown on rigid and flexible polycrystalline yttria-stabilized zirconia by pulsed laser ablation (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 223-227 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ growth of highly oriented YBa2Cu3O7−x thin films (200–500 nm in thickness) has been obtained by pulsed KrF (248 nm) laser ablation on both rigid and flexible randomly oriented polycrystalline yttria-stabilized zirconia substrates. It is shown that c-axis-perpendicular YBa2Cu3O7−x films with a mosaic spread of only 1.0° can be grown on these randomly oriented polycrystalline substrates. Superconducting thin films were obtained with Tc(R=0)∼89 K on well-polished substrates. For the films deposited on the flexible substrates, the superconducting Tc is not degraded by repeated bending of the flexible substrate/film composite over a 2.25-cm-radius arc although the normal-state resistivity increases slightly, suggesting the creation of microcracks. The YBa2Cu3O7−x films grown on rigid polycrystalline yttria-stabilized zirconia substrates have a critical current density Jc(H=0)∼1400 A/cm2 at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347121
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  • 3
    Electronic Resource
    Electronic Resource
    The adhesion of metallic films to laser-irradiated alumina (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5176-5179 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The adhesion strength of copper and nickel films deposited onto polycrystalline alumina (Al2O3) substrates is greatly increased by pulsed ultraviolet excimer (XeCl, 308 nm) laser irradiation of the alumina prior to metal-film deposition. Adhesion enhancement occurs for pulsed-laser energy densities, Ed, both below and above alumina's melting threshold (Edth∼0.7 J/cm2). Cross-section transmission electron micrographs of alumina irradiated at Ed(approximately-greater-than) Edth reveal an outer amorphous layer 40–60 nm thick that is formed during the rapid solidification process that follows pulsed-laser melting. Our results for gold, copper, and nickel films demonstrate that several factors contribute to metal-alumina bonding: (1) the chemical nature of the metal, as indicated by quite different adhesion strengths of sputter-deposited metals on unirradiated alumina substrates: 0.1 MPa for Au, 13 MPa for Cu, and 32 MPa for Ni; (2) the type and extent of laser-generated disorder/damage, since for gold significant bonding enhancement is obtained only if pulsed-laser melting of the alumina occurs; and (3) the irradiation atmosphere, as the adhesion strength of these metals to alumina is greatest if pulsed-laser irradiation is performed in an oxidizing atmosphere. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359264
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  • 4
    Electronic Resource
    Electronic Resource
    Heteroepitaxial growth of Ge films on (100) GaAs by pyrolysis of digermane (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 858-860 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pyrolysis of high-purity digermane (Ge2 H6 ) has been used to grow epitaxial Ge films of high crystalline quality on (100) GaAs substrates in a low-pressure environment. X-ray double-crystal diffractometry shows that fully commensurate, coherently strained epitaxial Ge films can be grown on (100) GaAs at digermane partial pressures of 0.05–40 mTorr for substrate temperatures of 380–600 °C. Amorphous films also were deposited. Information about the crystalline films surface morphology, growth mode, and microstructure was obtained from scanning electron microscopy, cross-section transmission electron microscopy, and in situ reflectivity measurements. The amorphous-to-crystalline transition temperature and the morphology of the crystalline films were both found to depend on deposition conditions (primarily the incidence rate of Ge-bearing species and the substrate temperature). Epitaxial growth rates using digermane were found to be about two orders of magnitude higher than rates using germane (GeH4 ) under similar experimental conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101777
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  • 5
    Electronic Resource
    Electronic Resource
    High critical current densities in YBa2Cu3O7−x films on polycrystalline zirconia (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1164-1166 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the growth on polycrystalline yttria-stabilized zirconia substrates of YBa2Cu3O7−x films with Jc (77 K)=11 000 A/cm2 and Jc (4.2 K)=122 000 A/cm2 by pulsed laser ablation. These Jc values are among the highest reported for YBa2Cu3O7−x on any polycrystalline substrate and approach the intrinsic upper limit for films with large-angle grain boundaries, as indicated by recent bicrystal experiments. We find that the substrate temperature during film growth is most important in obtaining high Jc polycrystalline films. Although the magnetic field dependence of Jc indicates the presence of weak links, the behavior of Jc (4.2 K, H) suggests that a percolative path consisting of low-angle grain boundaries exists in the films, resulting in Jc (4.2 K, 60 kOe)=4100 A/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104226
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  • 6
    Electronic Resource
    Electronic Resource
    Rapid heteroepitaxial growth of Ge films on (100) GaAs by pulsed supersonic free-jet chemical beam epitaxy (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1008-1010 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Very high epitaxial growth rates (0.25 μm/s), not attainable by conventional vapor phase film growth methods, have been obtained using a pulsed supersonic free jet to supply digermane (Ge2H6) for thermal decomposition at a heated (100)GaAs surface. Double-crystal x-ray diffractometry and scanning electron microscopy show that highly planar, smooth, and commensurate epitaxial Ge films are grown on (100)GaAs using gas pulses of 250 ms duration at 1–3 atm (0.1–0.3 MPa) pressure for substrate temperatures of 480–680 °C. It is believed that the very high growth rates effectively "freeze'' the Ge-GaAs interface resulting in minimal interfacial diffusion and reduced incorporation of impurities from the surrounding growth environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102261
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  • 7
    Electronic Resource
    Electronic Resource
    In-plane aligned CeO2 films grown on amorphous SiO2 substrates by ion-beam assisted pulsed laser deposition (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2012-2014 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Both (001)- and (111)-oriented CeO2 thin films have been grown on amorphous fused silica (SiO2) substrates by ion-beam assisted pulsed laser ablation of a polycrystalline CeO2 target. Using 200 eV Ar+ ions incident at 55° to the substrate normal, the preferred orientation for CeO2 film growth is (001) at room temperature, but changes to (111) for temperatures ≥300 °C. Furthermore, the ion-beam assisted CeO2 films exhibit strong in-plane crystallographic alignment. In contrast, CeO2 films grown without ion-beam assistance exhibit a mixture of polycrystalline orientations with the relative amounts depending on growth temperature. Under optimum conditions, off-normal-incidence Ar+ ions produce a (111)-oriented crystalline CeO2 film that is aligned with respect to a single in-plane axis, on an amorphous substrate. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112847
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  • 8
    Electronic Resource
    Electronic Resource
    Pulsed-laser ablation growth of epitaxial ZnSe1−xSx films and superlattices with continuously variable composition (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3008-3010 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a new method to grow epitaxial semiconductor alloys with continuously variable composition, while using a single pulsed laser ablation target of fixed composition. Epitaxial ZnSe1−xSx films with continuously variable sulfur content, x, were grown by ablating a ZnSe target through low-pressure ambient H2S gas. The sulfur content was easily controlled in the range 0〈x〈0.18 by varying the H2S partial pressure from 0 to 45 mTorr, for films grown at 325 °C. ZnSe1−xSx films differing in composition by as much as x=0.52 from the pure ZnSe target have been grown at 400 °C. We have used this method to grow heteroepitaxial structures with continuously graded or periodically repeating, abrupt compositional changes (compositional superlattices). This development removes the principal barrier to pulsed-laser ablation (PLA) growth of compositionally graded semiconductor thin-film materials, namely that the film and target normally have the same composition. The method appears to have broad application for PLA growth of other compound semiconductor films and heterostuctures, as well as to dope individual layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110267
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  • 9
    Electronic Resource
    Electronic Resource
    Enhanced superconducting properties in ultrathin YBa2Cu3O7−δ layers (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1432-1434 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The superconducting properties of ultrathin c-axis-oriented YBa2Cu3O7−δ(YBCO) layers can be significantly enhanced by use of more conductive buffer and cap layers. In particular, Pr0.5Ca0.5Ba2Cu3O7−δ/YBCO/Pr0.5Ca0.5Ba5 Cu3O7−δ trilayer structures, with YBCO layer thickness as small as 1 unit cell, have superior transport properties to PrBa2Cu3O7−δ/YBCO/PrBa2Cu3O7−δ structures, including an increase in Tc and a narrower superconducting transition. The enhanced superconducting properties that result from using Ca-(hole) doped buffer and cap layers may be a result of a diminished perturbation of the order parameter at growth-related steps in the electrical continuity of the YBCO layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109648
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  • 10
    Electronic Resource
    Electronic Resource
    Structural and electrical properties of La0.5Sr0.5CoO3 epitaxial films (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2045-2047 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial La0.5Sr0.5CoO3 films with very smooth surface morphology were grown on (100) SrTiO3 and (100) MgO substrates by pulsed laser deposition. Scanning tunneling microscopy reveals that the thin film is formed by the coalescence of many aligned square mesas. The growth proceeds from the edges of terraces which are stacked on the mesa. Spiral growth is never observed. Films display an crystallographically isotropic metallic-like electrical conductivity but become semiconductor-like after vacuum annealing. The energy for carrier activation is 0.3 eV. The change of the electrical resistivity of La0.5Sr0.5CoO3 with oxygen pressure at high temperature is much less sensitive than that of YBa2Cu3O7−x.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109474
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