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  • 1
    Electronic Resource
    Electronic Resource
    The absolute absorption strength and vibrational coupling of CH stretching on diamond C(111) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 7411-7421 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This research investigates the infrared absorption intensity and isotope-dependent frequency shifts of CH stretching on diamond C(111) single-crystal surfaces by Fourier transform infrared spectroscopy (IRS). By employing single-pass direct absorption and in situ surface oxidation methods, a single sharp feature at νm=2832.2±0.9 cm−1 with a FWHM of Γ(approximate)6 cm−1 is observed at 800 K. Systematic measuring of how band intensity depends on hydrogen etching time indicates that a well hydrogen-terminated C(111)-1×1 can be prepared only after prolonged exposure of the surface to H, generated by hot W filaments, at 1100 K. A study of the band intensity at saturation, and assuming an electronic polarizability of αe=0.65 Å3 for the CH bond as that in CH4, yields an integrated cross section σ¯z=5.5×10−18 cm for the CH stretching motion along the internuclear axis. Additional measurements of band position as a function of mixed isotope concentrations afford a stretching frequency of νi=2816.2±0.9 cm−1 for a single CH isolated in a monolayer of CD oscillators at 800 K. The frequency shift of νm−νi=16.0 cm−1 is too large for dipole coupling theories to explain. The implications of the present findings with regard to applying IRS for quantitatively characterizing CVD diamondlike carbon films are discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473701
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  • 2
    Electronic Resource
    Electronic Resource
    Exciton Level Structure and Dynamics in the CP47 Antenna Complex of Photosystem II (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 7717-7724 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100082a050
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  • 3
    Electronic Resource
    Electronic Resource
    On the Question of the Chlorophyll a Content of the Photosystem II Reaction Center (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 7725-7735 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100082a051
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  • 4
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance and phase decomposition of Fe–XCr–Co (WFe/WCo=1) thin film granular alloys (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4523-4527 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study, the giant magnetoresistance (MR) effect was observed in Fe–XCr–Co (WFe/WCo=1, X=27, 40, 50, 60, 70, and 80 wt %) ternary heterogeneous alloy films. After aging, the separated phases and lattice images of the α1 (Fe–Co rich phase) and α2 (Cr rich phase) were further determined by high resolution transmission electron microscope. Experimental results indicate that the MR variations in Fe–Cr–Co thin films alloys were associated with the heterogeneous microstructure. By isothermal aging at 550 °C for 80 min, the largest MR of −43% appears for the film with the composition of 40(Fe/Co)–60Cr at 77 K under a field of 14 kOe. At the same treatment condition, the MR ratios of 50(Fe/Co)–50Cr and 30(Fe/Co)–70Cr are −13.2% and −21.3%, respectively. Cr content, therefore, significantly affected the MR ratio. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363557
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  • 5
    Electronic Resource
    Electronic Resource
    The magnetoresistance and microstructure of Fe–xCr–10Co alloy thin films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8593-8597 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Large negative magnetoresistance (MR) is observed in Fe–xCr–10Co (x=10,20,30,40,50,- 60,70, and 80 wt %) ternary heterogeneous alloy films prepared by the IBS (ion beam sputter) deposition process. All the as-deposited films consisted of the α phase alone. After aging treatment, the α phase is decomposited into two phases: the α1 (Fe–Co rich phase) and α2 (Cr rich phase). In the granular alloy, the GMR effect is obtained by virtue of the interface scattering between α1 and α2. After isothermal aging at 400 °C for 1 h, the largest MR of −27% appears around the Cr content of 60 wt % at 77 K and 14 kOe. The MR ratio of Fe–50Cr–10Co and Fe–70Cr–10Co is −12% and −20%, respectively, at the same condition. The MR ratio is also obviously effected by the Cr (or Fe) content in the alloy system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362455
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  • 6
    Electronic Resource
    Electronic Resource
    The vibrational dephasing and relaxation of CH and CD stretches on diamond surfaces: An anomaly (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 3975-3983 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The temperature dependence of infrared absorption spectra of CH and CD on diamond nanocrystal surfaces has been investigated. Phase relaxation was closely examined by analyzing frequency shifts and line broadening in the spectra. Based on the model of Persson and Ryberg [Phys. Rev. B 40, 10 273 (1989)], coupling phonons responsible for the pure dephasing process were found to resonate at ω0≈1200 cm−1 for the CH stretch. By including both the phase and energy relaxation in the linewidth analysis and assuming that energy relaxes via three-phonon emission, we estimate a pure dephasing time of T*2≈340 ps at room temperature. This value is one order of magnitude larger than the energy relaxation time, T1≈19 ps, measured by Chin et al. [Europhys. Lett. 30, 399 (1995)] on a C(111) single crystal surface. We interpret the anomalous observation to be the result of the high frequency of the coupling phonons. For the CD stretches, however, severe line broadening due to exceedingly rapid energy relaxation disallows accurate determination of T*2. Since CH and CD stretches have similar thermal and inhomogeneous broadening characteristics, the lifetime of the latter is estimated to be T1≈220 fs. This T1 value is one of the shortest vibrational energy relaxation times for any adsorbate on a dielectric surface. Systematic comparison of these anomalous results with the measurements of SiH stretches on Si(100) and Si(111) is given. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472271
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  • 7
    Electronic Resource
    Electronic Resource
    Optical and structural studies of the effect of spacers in modulation-doped ZnSe/Zn1−xCdxSe quantum wells (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 891-895 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of spacers in modulation-doped Zn1−xCdxSe/ZnSe:Cl multiple quantum wells (MD-MQWs) was investigated by photoluminescence (PL) and time-of-flight secondary-ion-mass spectrometry (TOF-SIMS). A comparison was made between structures with and without spacers as a function of annealing temperature. The diffusion of Cl and Cd was monitored by TOF-SIMS depth profiling and photoluminescence. Although TOF-SIMS does not show any significant diffusion of Cl and Cd in both structures at temperatures up to 385 °C, the PL results indicate the modification of optical properties in the Zn1−xCdxSe/ZnSe:Cl MD-MQWs due to annealing. Up to an annealing temperature of 385 °C, the MD-MQWs with spacers show superior optical quality in the quantum well regions, while quenching of the quantum well band-edge PL and strong enhancement of deep-level emission were observed from the MD-MQWs without spacers. This phenomenon suggests that the radiative deep-level emission may provide more efficient channel for electron–hole recombination with increasing annealing temperature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370863
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of heat treatment and Co on the giant magnetoresistance of Fe-60 Cr–XCo alloy thin films (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 317-321 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article presents the giant magnetoresistance (GMR) effect and microstructure of Fe-60Cr-XCo ternary heterogeneous alloy films. After ion beam sputtering, the films are heat treated at a temperature within the miscibility gap. The separated phases and lattice images of the α1 (Fe–Co rich phase) and α2 (Cr rich phase) are further determined by high resolution transmission electron microscopy. In the granular alloy, the GMR effect is obtained by the interface scattering between the phases of α1 and α2. By isothermal aging at 550 °C for 80 min, the largest MR ratio of −62% appears for the film with the composition of Fe-60Cr-15Co at 77 K under a field of 14 kOe. For the same treatment, the MR ratios of Fe-60Cr-10Co and Fe-60Cr-20Co are −39% and −43%, respectively. The Co content and heat treatment condition in the alloy system obviously affect the MR ratio. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365814
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  • 9
    Electronic Resource
    Electronic Resource
    Infrared spectroscopy of adsorbed CO2 as a probe for the surface heterogeneity of diamond C(111)-1×1:H (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2474-2476 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Infrared polarization spectroscopy of the stretching motion of physisorbed CO2 has been used as a probe for the heterogeneity of hydrogen-terminated diamond single crystal surfaces. At the substrate temperature of 83 K, band shape, photometry, and isotherm measurements all indicate that the CO2 molecules are first adsorbed on defect sites, followed by adsorption on terraces that yields a single sharp spectral feature at 2333 cm−1 with FWHM=6 cm−1. Nearly 20% of the surface sites on the as-polished C(111)-1×1:H surfaces are defects © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114612
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  • 10
    Electronic Resource
    Electronic Resource
    Studies of ZnSe-based semiconductor thin films using grazing incidence x-ray scattering and diffraction (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 237-243 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Grazing incidence x-ray scattering and x-ray diffraction techniques have been employed to investigate the microstructures in various ZnSe-based semiconductor thin films grown on GaAs substrates by molecular beam epitaxy and metalorganic chemical vapor deposition methods. The results are also used for a comparison of the interfacial roughness and overall quality of the II–VI thin films prepared by these two different growth methods. Structural parameters such as the interfacial roughness and layer thickness obtained from the scattering measurements and lattice constants obtained from the x-ray diffraction pattern around the GaAs(004) peak can be correlated with the film deposition rate, compound composition, and lattice strain in the epilayers. We thus demonstrate that x-ray scattering techniques in conjunction with diffraction measurements are useful tools for nondestructive characterization of buried interfaces in semiconductor layer materials. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369434
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