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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 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
    Control of domain structure of epitaxial PbZr0.2Ti0.8O3 thin films grown on vicinal (001) SrTiO3 substrates (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2805-2807 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the polydomain formation in 100–200-nm-thick PbZr0.2Ti0.8O3 epitaxial thin films on vicinally cut (100) oriented SrTiO3 substrates. Our results show that there is a preferential location of the nucleation of the a domains along the step edges of the underlying substrate. By piezo-response microscopy, we show that all a domains have their polarization aligned along the same direction. This result is in contrast to flat substrates where fourfold symmetry of a domains is observed. We observe that the critical thickness for a domain formation is much lower than that for PbZr0.2Ti0.8O3 films grown on flat substrates. We have developed a model based on minimization of elastic energy to describe the effect of localized stresses at step edges on the formation of a domains in the ferroelectric layer. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402645
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  • 8
    Electronic Resource
    Electronic Resource
    Dielectric properties in heteroepitaxial Ba0.6Sr0.4TiO3 thin films: Effect of internal stresses and dislocation-type defects (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1695-1697 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of heteroepitaxial Ba0.6Sr0.4TiO3 were grown on 0.29(LaAlO3):0.35(Sr2TaAlO6) substrates using pulsed-laser deposition. X-ray characterization revealed compressive in-plane stresses in the thinnest films, which were relaxed in a continuous fashion with increasing thickness. A theoretical treatment of the misfit strain was in good agreement with the measured out-of-plane lattice parameter. The low-frequency dielectric constant was measured to be significantly less than the bulk value and found to decrease rapidly for films less than 100 nm. A thermodynamic model was developed to understand the reduction in dielectric constant. By observing the microstructure using plan-view and cross-section transmission electron microscopy, we identified local strain associated with a threading dislocation density on the order of 1011 cm−2 as a possible mechanism for dielectric degradation in these films. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1308531
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  • 9
    Electronic Resource
    Electronic Resource
    Growth and characterization of II–VI blue light-emitting diodes using short period superlattices (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 379-381 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the properties of II–VI short period superlattice (SPSL) blue light-emitting diodes grown by molecular beam epitaxy. The device consists of a ZnSe active layer, SPSL MgZnSSe cladding layers, and a ZnSeTe digital graded contact. The SPSL structure is made of alternating layers of MgSe, ZnSe, ZnS, and ZnSe. Highly ordered SPSL layer structures are successfully grown. Tweedlike contrast is observed in the pseudomorphic SPSL from our transmission electron microscopy analysis. The device shows high purity blue emission at 460 nm at room temperature with a 13 nm full width at half maximum. Operating at 14 A/cm2, the half-intensity lifetime is more than 13 h at room temperature with an external quantum efficiency of ∼0.1%. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116691
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxy of low defect density (≤1×104 cm−2) ZnSSe on GaAs (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2828-2830 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the growth of pseudomorphic ZnSSe layers on GaAs. The dependence of the epilayer quality on Zn exposure to the GaAs surface is investigated. Zn treatment prior to the ZnSe buffer growth on the As-rich GaAs surface results in the lowest defect density. Transmission electron microscopy studies show that an atomic scale smooth interface is formed. Based on the etch pit density and photoluminescence image analysis, ZnSSe layers with defect density ≤1×104 cm−2 can be reproducibly obtained. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116338
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