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  • 1
    Electronic Resource
    Electronic Resource
    Thickness dependence of structural and electrical properties in epitaxial lead zirconate titanate films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 595-602 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the effect of misfit strain on the microstructure and properties of ferroelectric lead zirconate titanate thin films. We have changed the misfit strain by varying the film thickness and studied the thickness effect on the domain formation of epitaxial PbZr0.2Ti0.8O3 (PZT) films grown by pulsed laser deposition on (001) LaAlO3 substrates with La0.5Sr0.5CoO3 (LSCO) electrodes. The nominal thickness of the PZT films was varied from 60 to 400 nm with the LSCO electrode thickness kept constant at 50 nm. X-ray diffraction experiments show that the films relax via the formation of a domains, the fraction of which increase with the ferroelectric film thickness. The c-axis lattice constant of PZT films calculated from the 002 reflection decreases with increasing film thickness and approaches the bulk value of ∼0.413 nm in the films thicker than 300 nm. Cross-sectional transmission electron microscopy images reveal that the a-domain fraction and period increase with increasing film thickness. The relaxation of misfit strain in the film is accompanied by systematic changes in the polarization properties, as well as the switching fields, quantified by the coercive field and the activation field. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370772
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of the optical constants of ZnSe films by spectroscopic ellipsometry (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 514-517 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spectroscopic ellipsometry was used to determine the real and imaginary parts of the dielectric function of ZnSe thin films grown on (001) GaAs substrates by molecular-beam epitaxy, for energies between 1.5 and 5.0 eV. A sum of harmonic oscillators is used to fit the dielectric function in order to determine the values of the threshold energies at the critical points. The fundamental energy gap was determined to be at 2.68 eV. The E0+Δ0 and E1 points were found to be equal to 3.126 and 4.75 eV, respectively. Below the fundamental absorption edge, a Sellmeir-type function was used to represent the refractive index. At the critical points, E0 and E0+Δ0, the fitting was improved by using an explicit function combining the contributions of these two points to the dielectric function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358484
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  • 3
    Electronic Resource
    Electronic Resource
    Superconducting and structural properties of Nd2−xCexCuO4−y thin films on perovskite and fluorite substrates (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2119-2124 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High quality epitaxial Nd2−xCexCuO4−y (NCCO) thin films were fabricated on various substrates by pulsed-laser deposition using N2O reactive gas. The similarities and dissimilarities of the superconducting and structural properties of NCCO films, on perovskite-type substrates such as LaAlO3, NdGaO3, and SrTiO3 and on a fluorite-type substrate of yttria-stabilized zirconia (YSZ), were investigated systematically as a function of film thickness by transport measurements and structural analysis. A remarkable reduction of Tc was observed when the film was thinner than a critical thickness, which strongly depends on the substrate. The critical thicknesses for which Tc is 80% of Tc max are 1200, 1000, 600, and 450 A(ring) for LaAlO3, NdGaO3, SrTiO3, and YSZ, respectively. YSZ turns out to be the best candidate for the growth of very thin NCCO films among the substrates studied. These results show a strong correlation between the strain and Tc in NCCO thin films and point the way to the fabrication of n-type superconducting electric field devices using ultrathin NCCO films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356318
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  • 4
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance peaks in CoNiCu/Cu multilayers grown by electrodeposition : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6519-6521 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Giant magnetoresistance (GMR) of CoNiCu/Cu multilayers grown by electrodeposition was measured as a function of the copper layer thickness and effects of the order of 14% were obtained. The copper layer thickness ranged from 0.7 to 3.5 nm. Two peaks in the magnetoresistance were observed. One was centered at a copper thickness of ∼1.0 nm and the second was centered at ∼2.3 nm. Comparison of the field dependence of the magnetoresistance with the field dependence of the magnetization, as determined by vibrating-sample magnetometer, suggests that the saturation field for GMR and the magnetization are similar for the larger copper thicknesses, but are strikingly different near 1.0 nm copper thickness. This observation suggests that the GMR is affected by different factors depending on the thickness of the copper layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358250
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructural properties of (ZnSe/FeSe) and (ZnSe/MnSe) diluted magnetic semiconductor superlattices (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5195-5195 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, there has been increased research activity on Fe-, Mn-, and Co-based diluted magnetic semiconductors (DMS) because of their interesting magneto-optical properties. Potential applications of DMS usually require thin films with a high degree of structural perfection, and high quality single crystal epilayers of Zn1−xFexSe and Zn1−xCoxSe have been grown by molecular beam epitaxy (MBE). In this work, the microstructural properties of (ZnSe/FeSe) and (ZnSe/MnSe) DMS superlattices grown on (001) GaAs substrates by MBE have been investigated using transmission electron microscopy. High-quality (ZnSe/FeSe) superlattices were grown by introducing a ZnSe buffer layer on the GaAs substrate prior to the growth of the superlattice. In contrast, nominal (ZnSe/FeSe) superlattices grown directly without a buffer layer on the substrate showed evidence for interdiffusion between the constituent layers of the superlattice. Chemical ordering of the Zn and Fe atoms was also observed in the resultant Zn1−xFexSe alloys along the [001] and [110] directions. This ordered structure corresponds to the CuAu–I type structure. In contrast, the (ZnSe/MnSe) superlattices did not show interdiffusion, but contained many microtwins and 60°-type misfit dislocations. The MnSe layer in the (ZnSe/MnSe) superlattices existed as a zinc-blende structure. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361337
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  • 6
    Electronic Resource
    Electronic Resource
    Structural and magnetic fourfold symmetry of Co/Cu multilayers electrodeposited on Si(001) substrates (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1504-1507 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed in-plane fourfold symmetry of the magnetization and magnetoresistance in Co/Cu multilayers electrodeposited on Si(001) substrates covered with a thin evaporated Cu seed layer. The fourfold symmetry correlates with the in-plane crystalline structure of the multilayers. High-angle x-ray diffraction shows that the Co/Cu multilayers have a strong (001) texture. Φ-scan x-ray diffraction reveals that the multilayers have fourfold symmetry in the plane with a 45° rotation with respect to the Si substrates. We estimated an anisotropy field of 98 mT from vector magnetization curves, which is in fairly good agreement with the value obtained from Co/Cu multilayers electrodeposited on (001) Cu single crystal substrates. The giant magnetoresistance appears to depend on the in-plane orientation of the multilayer due to the magnetocrystalline anisotropy. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368254
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  • 7
    Electronic Resource
    Electronic Resource
    Misfit dislocation nucleation in doped and undoped ZnSe/GaAs (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3197-3199 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed that undoped ZnSe films grown on GaAs substrates by molecular beam epitaxy show an irregular array of interfacial 60° misfit dislocations. However, N and Cl doping of the ZnSe thin films changes the interfacial dislocation structure. p-type ZnSe with N concentrations of ∼1018/cm3 shows a regular array of interfacial 60° misfit dislocations and a lower (∼1×106/cm2) density of threading dislocations compared to undoped films. However, samples with doping levels higher than 1019/cm3 show a density of threading dislocations of ∼108/cm2. These differences are explained in terms of Frank partial dislocations observed only in doped ZnSe. The Frank partial dislocations act as nucleation sites for the misfit dislocations. Thus, different mechanisms for the formation of misfit dislocations in doped and undoped films occur in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110197
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  • 8
    Electronic Resource
    Electronic Resource
    Microstructure of laser-deposited superconducting Nd1.85Ce0.15CuO4−y films (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3022-3024 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The morphology and microstructure of Nd1.85Ce0.15CuO4−y (NCCO) films grown epitaxially on (100) LaAlO3 (LAO) by pulsed laser deposition were studied by selected-area electron diffraction and high-resolution electron microscopy. The films were composed primarily of c-axis oriented grains and did not contain any polytypoidic faulting. The in-plane epitaxial relationship of the films was found to be [100]NCCO //[001]LAO. The Nd1.85Ce0.15CuO4−y-LaAlO3 interface is sharp and free of defects. A weak peak around the (110) position of NCCO(T') structure in x-ray diffraction was observed. Using microdiffraction and energy-dispersive x-ray analysis, we confirmed that this peak corresponds to the (004) reflection of cubic Ce0.5Nd0.5O1.75.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109177
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  • 9
    Electronic Resource
    Electronic Resource
    Chemical ordering in Zn1−xFexSe alloys (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2302-2304 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed chemical ordering in Zn1−xFexSe (x≈0.5) epilayers as well as in nominal (ZnSe/FeSe) superlattices along the [001] growth direction and the [110] direction using transmission electron microscopy. The ordered structure consists of alternating ZnSe and FeSe layers along the [001] and [110] directions. In nominal (ZnSe/FeSe) superlattices grown on (001) GaAs substrates, strain-induced interdiffusion between the layers takes place followed by ordering of the resultant Zn1−xFexSe alloys. Computer simulated images for a Zn0.5Fe0.5Se compound were obtained and compared with experimental images. To our knowledge, this is the first observation of ordering in a II-VI alloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108271
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  • 10
    Electronic Resource
    Electronic Resource
    Strain effects on the energy bands of ZnSe films grown on GaAs substrates by spectroscopic ellipsometry (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3620-3622 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room-temperature spectroscopic ellipsometry measurements were carried out on ZnSe thin films grown on (001)GaAs substrates by molecular-beam epitaxy for the study of the lattice mismatch-induced strain at the interface. The magnitude of the absorption coefficient at the E0+Δ0 critical point is very sensitive to the strain in the film. The variation in the magnitude of the absorption coefficient is used to estimate the critical thickness for the onset of dislocation generation. Almost complete relaxation of the films was obtained for thicknesses higher than 500 nm. Also, the strain-induced coupling between the valence subbands was found to cause additional shifting of the light-hole subband.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111223
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