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  • 1
    Electronic Resource
    Electronic Resource
    Growth and characterization of (111) and (001) oriented MgO films on (001) GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3276-3283 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of substrate preparation on the structure and orientation of MgO films grown on (001) GaAs using pulsed laser deposition has been investigated. Textured MgO films displaying a (111)MgO(parallel)(001)GaAs orientation relation with x-ray rocking curve full width at half maximum (FWHM) values as low as 1.8° were obtained in cases where the native GaAs surface oxide was only partially desorbed prior to growth. Reflection high-energy electron diffraction, transmission electron microscopy (TEM), and x-ray pole figure analysis of these films reveals a preferential orientation within the plane of the substrate: [11¯0]MgO(parallel)[11¯0]GaAs and [112¯]MgO(parallel)[110]GaAs. An interfacial layer (∼5 nm thick) was observed in high resolution TEM analysis, and was attributed to a remnant native GaAs oxide layer. Complete desorption of the native GaAs oxide at ∼600 °C in vacuum prior to MgO growth led to significant surface roughening due to Langmuir evaporation, and resulted in randomly oriented polycrystalline MgO films. Growth of MgO on Sb-passivated GaAs substrates, which provided smooth, reconstructed surfaces when heated to 350 °C in vacuum, resulted in cube-on-cube oriented films [i.e., (001)MgO(parallel)(001)GaAs,[100]MgO(parallel)[100]GaAs] with x-ray rocking curve FWHM values as low as 0.47°. TEM analysis of the cube-on-cube oriented films revealed evidence of localized strain fields at the MgO/GaAs interface, indicating the presence of misfit dislocations in the MgO layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352975
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  • 2
    Electronic Resource
    Electronic Resource
    Hierarchical domain structures and in situ domain migration in the antiferroelectric ceramic PLSnZT (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7261-7267 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystallography and microstructure of an antiferroelectric ceramic of approximate composition Pb0.97La0.02(Zr0.65Sn0.25Ti0.10)O3 have been examined. Transmission electron microscopy (TEM), x-ray, and neutron powder studies were carried out. The cell is metrically tetragonal with a c/a ratio of 0.993 when indexed to the parent cubic perovskite cell. The structure exhibits both a commensurate supercell, believed to be associated with oxygen octahedra distortions, and an incommensurate modulation. The different crystallographic variants of the tetragonal antiferroelectric phase gave rise to a hierarchy of domain structures. Charging of TEM specimens having an incomplete conductive coating caused domain migration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354014
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  • 3
    Electronic Resource
    Electronic Resource
    Observation of gold evaporated on graphite (00.1) cleaved surfaces (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6520-6522 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gold evaporated on air-cleaved (00.1) graphite was observed by scanning tunneling microscopy. Most individual gold islands were not stable during scanning; some islands even appeared to translate. These observations suggest that the interaction between the gold islands and the scanning tunneling microscope tip is stronger than that between the gold and the air-cleaved graphite substrate. Some gold islands were observed to be stable. It was deduced that stable islands at steps were located on the upper layer rather than on the lower layer. It is also deduced that the alignment of the elongated gold grains in the continuous film may be related to cleavage steps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346856
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  • 4
    Electronic Resource
    Electronic Resource
    Mechanics of laser-assisted debonding of films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1527-1536 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Films of GaN and ZnO can be separated from the substrates on which they are grown by the use of a laser-assisted debonding process in which a pulsed laser is shone through the substrate and absorbed in the film. Experience shows that the success in separating the films intact and damage free depends sensitively on the laser parameters used and the physical and geometric properties of the films. In this contribution, the mechanics of the laser-assisted debonding of GaN films are presented and used to construct process maps that delineate the conditions for damage-free film separation. The key variable is the nondimensional group ΩEp/(dp2τ), where Ω is a lumped material constant, Ep is the laser pulse energy, dp is the diameter of the illuminated area and τ is the laser pulse length. Experimental observations of UV/excimer laser assisted debonding of GaN films from sapphire substrates are used to illustrate the types of deformations and cracking modes on which the process maps are based. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1338519
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  • 5
    Electronic Resource
    Electronic Resource
    Cracking of GaN films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1025-1034 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cracking of thick GaN films grown on sapphire is reexamined on the basis of a combination of microstructural observations of cracking and established mechanics of fracture of films. It is argued that cracking is motivated by tensile growth stresses once a critical thickness is reached. Subsequent growth on the cracked films occurs, perpetuating the cracked structure until the crack surfaces approach one another and touch. Continued film growth buries the crack. Once the crack faces touch, there are conditions under which it is energetically favorable for the cracks to close and heal. Crack healing can be kinetically limited. Whether the crack healing is complete within the growth time depends on several factors including, it is suggested, whether impurities have adsorbed to the surface during growth. Conditions under which cracks that have extended into the sapphire substrate during film growth can act as critical flaws for fracture of the substrate on cooling are also presented. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1330243
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  • 6
    Electronic Resource
    Electronic Resource
    Moisture diffusion along the TiN/SiO2 interface and in plasma-enhanced chemical vapor deposited SiO2 (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3695-3698 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusivity of moisture along the TiN/SiO2 interface has been determined by imaging the inward diffusion of 18O and 2D from isotopically labeled water using a secondary ion mass spectroscopy (SIMS) technique. The diffusivity, at room temperature, of the 18O and 2D labeled species along the interface are indistinguishable and have a value of 6.0±2.0×10−13 cm2/s, four orders of magnitude faster than bulk diffusivity of the same species in the plasma-enhanced chemical vapor deposition silica, also determined by SIMS. From 8 to 90 °C, the activation energies for interface and bulk diffusivities of the 2D labeled species are found to be 0.21 and 0.74 eV, respectively. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289481
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  • 7
    Electronic Resource
    Electronic Resource
    Dielectric cracking produced by electromigration in microelectronic interconnects (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6302-6312 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The development of stress during electromigration along Al lines, constrained within a dielectric in a coplanar test configuration, is measured. It is shown that, above a certain threshold current density, cracking of the dielectric is induced in the vicinity of the anode. Cracking of the dielectric leads to loss of mechanical constraint on the aluminum conductor which, in turn, leads to increases in electrical resistance with continued current flow. The electromigration-induced stresses are determined from the measured frequency shifts induced in a novel ruby strain sensor embedded immediately beneath the interconnect line on a sapphire substrate. The transparency of the sapphire substrate also facilitated the observation of a hitherto unreported form of dielectric cracking, namely cracking from the interconnect along internal interfaces. The observations of dielectric cracking are in agreement with a recent fracture mechanics model. Analysis of the stress data, together with the results of finite element calculations of the strain energy release rate for crack extension, gives a quantitative estimate of the effective valence Z*(=1.3±0.2) for aluminum. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289044
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  • 8
    Electronic Resource
    Electronic Resource
    Piezoelectric contributions to the electrical behavior of ZnO varistors (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4430-4438 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Internal stresses exist in ZnO varistors as a result of both crystallographic anisotropy in thermal expansion of the constituents and thermal expansion mismatch between phases. Due to the piezoelectric nature of ZnO, these stresses induce a net electric dipole moment that modifies the grain boundary Schottky barriers and causes an alteration of the varistor current–voltage response in the nonlinear regime. We report Raman piezospectroscopic measurements of residual strains in polycrystalline ZnO and develop a stochastic model for the distribution of potential barrier heights based on the distribution of internal stresses. The model provides a physical basis for barrier height distributions used in electrical network simulations of varistor transport behavior. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373088
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  • 9
    Electronic Resource
    Electronic Resource
    Crack formation in epitaxial [110] thin films of YBa2Cu3O7−δ and PrBa2Cu3O7−x on [110]SrTiO3 substrates (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1682-1684 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A characteristic feature of epitaxial [110] thin films of YBa2Cu3O7−δ and PrBa2Cu3O7−x on [110]SrTiO3 substrates is that the films have a tendency to crack along the (001) planes. We have studied the crack spacing as a function of deposition temperature and film thickness. The experimental data have been found to be in excellent agreement with a theoretical analysis of the crack spacings in brittle films. The study has allowed us to determine the critical thickness below which no cracks are expected to form as a function of temperature for [110] films of YBa2Cu3O7−δ, PrBa2Cu3O7−x, and YBa2Cu3O7−δ/ PrBa2Cu3O7−x bilayers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105110
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  • 10
    Electronic Resource
    Electronic Resource
    Anomalous superperiodicity in scanning tunneling microscope images of graphite (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2396-2398 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An anomalously large periodicity has been observed in scanning tunneling microscope images of a (00.1) graphite sample. The unusual contrast has hexagonal symmetry, a periodicity of 7.7±0.2 nm and is superimposed on the usual a=0.246 nm atomic spacing of graphite. Current-voltage curves recorded in the scanning tunneling spectroscopy mode from the region showing the superperiodicity exhibit slightly more metallic behavior than those from neighboring normal regions. One possible explanation for the observed periodicity is that it is a rotational moiré pattern resulting from the overlap between a misoriented layer of graphite and the underlying graphite single crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102906
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