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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7818-7822 
    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
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6569-6585 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of ambient oxygen pressure on the synthesis of epitaxial YBa2Cu3O7−x films on (100) SrTiO3 substrates by post-deposition annealing of amorphous precursor films was studied for oxygen partial pressures pO2 between 1.0 and 8.0×10−5 atm and annealing temperatures between 890 and 650 °C. A pO2−1/T diagram containing recent literature data regarding YBa2Cu3O7−x oxygen stoichiometry, phase stability, and liquid-phase formation was compiled to provide guidance for the selection and interpretation of annealing conditions. The results evidence a strong dependency of growth properties on the oxygen pressure with enhanced c-oriented epitaxy at lower pO2 values. A particularly interesting result is the formation of predominantly c-oriented films at 740 °C and pO2=2.6×10−4 atm (0.2 Torr). Similar to YBa2Cu3O7−x films produced by in situ laser ablation at the same temperature and oxygen pressure, the films exhibited low ion channeling yields (χmin〈0.1) and a dense (smooth) surface morphology, while critical currents at 77 K were well in excess of 1 MA/cm2. From the observed systematic variation of structural film properties with synthesis conditions, annealing lines were derived indicating (T-pO2) combinations for either c- or a-oriented epitaxial growth. A comparison is made between these lines and synthesis conditions for in situ film growth as compiled recently by Hammond and Bormann [Physica C 162–169, 703 (1989)].
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2081-2086 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The damage formed by 1.25 MeV, self-ions in Si at liquid nitrogen temperature was studied. A dominant feature of the damage for moderate ion fluences is the presence of isolated amorphous regions over the range of the ions. The microstructure of this damage is detailed and formation mechanisms discussed. The amorphous regions are shown to give rise to strain in the surrounding crystal lattice which varies with ion dose in a complicated manner. The annealing behavior of the damage was studied and two distinct, low-temperature stages observed. Different mechanisms are shown to be responsible for each stage including a transient mechanism at 300 °C initiated by the release of defects from damage clusters, and enhanced crystallization of amorphous Si at 400 °C due to lattice stress.
    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 72 (1992), S. 3735-3740 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The metalorganic chemical vapor deposition technique has been successfully applied to the growth of epitaxial platinum thin films on (100) surfaces of single-crystal potassium tantalate (KTaO3) and strontium titanate (SrTiO3). Platinum thin films grown on KTaO3 (100) at a rate of 70 nm/h showed strong Rutherford backscattering spectroscopy (RBS)/channeling effects with a χmin of 4%. In-plane φ and θ-2θ scan x-ray diffraction analysis demonstrated the three-dimensional epitaxial alignment of the platinum film with the KTaO3 substrate. Transmission electron micrographs viewed in cross section provided additional information regarding the nature of the epitaxial Pt-KTaO3 interface. The room-temperature resistivity of a 60-nm-thick Pt film on KTaO3 (100) was 12.0 μΩ cm. X-ray diffraction and pole-figure analysis showed that in the case of Pt films deposited on either fused quartz or Si (100) surfaces, the resulting films were polycrystalline and were fully textured with 〈111(approximately-greater-than) orientations perpendicular to the substrate surfaces.
    Type of Medium: Electronic Resource
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  • 5
    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
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 396-401 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of hydrogen in enhancing the photoluminescence (PL) yield observed from Si nanocrystals embedded in SiO2 has been studied. SiO2 thermal oxides and bulk fused silica samples have been implanted with Si and subsequently annealed in various ambients including hydrogen or deuterium forming gases (Ar+4%H2 or Ar+4%D2) or pure Ar. Results are presented for annealing at temperatures between 200 and 1100 °C. Depth and concentration profiles of H and D at various stages of processing have been measured using elastic recoil detection. Hydrogen or deuterium is observed in the bulk after annealing in forming gas but not after high temperature (1100 °C) anneals in Ar. The presence of hydrogen dramatically increases the broad PL band centered in the near infrared after annealing at 1100 °C but has almost no effect on the PL spectral distribution. Hydrogen is found to selectively trap in the region where Si nanocrystals are formed, consistent with a model of H passivating surface states at the Si/SiO2 interface that leads to enhanced PL. The thermal stability of the trapped H and the PL yield observed after a high temperature anneal have been studied. The hydrogen concentration and PL yield are unchanged for subsequent anneals up to 400 °C. However, above 400 °C the PL decreases and a more complicated H chemistry is evident. Similar concentrations of H or D are trapped after annealing in H2 or D2 forming gas; however, no differences in the PL yield or spectral distribution are observed, indicating that the electronic transitions resulting in luminescence are not dependent on the mass of the hydrogen species. © 1999 American Institute of Physics.
    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 80 (1996), S. 6720-6724 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-quality ceramics based heteroepitaxial structures of oxide-nitride-semiconductors, i.e., SrTiO3/TiN/Si(100) have been fabricated by in situ pulsed laser deposition. The dependence of substrate temperature and oxygen partial pressure on the crystalline quality of the SrTiO3 films on Si with epitaxial TiN template has been examined. We found that epitaxial growth occurs on TiN/Si(100) above 500 °C, initially at a reduced O2 pressure (10−6 Torr), and followed by a deposition in the range of 5–10×10−4 Torr. X-ray diffraction (aitch-theta, ω, and Φ scans) and transmission electron microscope (TEM) results revealed an excellent alignment of SrTiO3 and TiN films on Si(100) with a cube-on-cube epitaxy. Rutherford backscattering and ion channeling results show a channeling minimum yield (χmin) of ∼13% for the SrTiO3 films. High-resolution TEM results on the SrTiO3/TiN interface show that the epitaxial SrTiO3 film is separated from the TiN by an uniform 80–90 A(ring) crystalline interposing layer presumably of TiNxO1−x (oxy-nitride). The SrTiO3 film fabricated at 700 °C showed a high relative dielectric constant of 312 at the frequency of 1 MHz. The electrical resistivity and the breakdown field of the SrTiO3 films were more than 5×1012 Ω cm and 6×105 V cm−1, respectively. An estimated leakage current density measured at an electric field of 5×105 V/cm−1 was less than 10−7 A/cm2. © 1996 American Institute of Physics.
    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 78 (1995), S. 4386-4389 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanocrystals of group-IV semiconductor materials (Si, Ge, and SiGe) have been fabricated in SiO2 by ion implantation and subsequent thermal annealing. The microstructure of these nanocrystals has been studied by transmission electron microscopy. Critical influences of the annealing temperatures and implantation doses on the nanocrystal size distributions are demonstrated with the Ge-implanted systems. Significant roughening of the nanocrystals occurs when the annealing temperature is raised above the melting temperature of the implanted semiconductor material. © 1995 American Institute of Physics.
    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 79 (1996), S. 1876-1880 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sequential ion implantation of As and Ga into SiO2 and α-Al2O3 followed by thermal annealing has been used to form zinc-blende GaAs nanocrystals in these two matrices. In SiO2, the nanocrystals are nearly spherical and randomly oriented, with diameters less than 15 nm. In Al2O3, the nanocrystals are three dimensionally aligned with respect to the crystal lattice. Infrared reflectance measurements show evidence for surface phonon modes in the GaAs nanocrystals in these matrices. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2174-2176 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of YBa2Cu3Ox thin films and YBa2Cu3Ox/PrBa2Cu3Ox superlattice films grown on (00L) SrTiO3 substrates has been studied using x-ray diffraction and transmission electron microscopy. The films consist of four symmetry-equivalent domains related by mutually perpendicular (hh0) and (hh¯0) twin boundaries. One twin orientation is often highly favored over the other. We have correlated this in-plane symmetry breaking with small miscuts of the substrate surface towards the [HH0] direction and propose that interfacial steps act as nucleation sites for twins. Thus, by controlling the surface normal, a technique is described for producing films containing aligned twin boundaries.
    Type of Medium: Electronic Resource
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