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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7266-7274 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed small- and large-angle x-ray scattering experiments on CdTe/MnTe superlattices. The Fresnel optical method and the distorted wave Born approximation were used to extract from small-angle measurements out-of-plane and in-plane information about the interfaces. Specular reflectivity shows that the interface roughness is quite high (about 7 Å) for all superlattices. The effective MnTe concentration, directly determined from the refractive index profile, is successfully used to simulate the structured nonspecular scattering, and to determine the lateral correlation length of the interface roughness (about 1500±750 Å). Moreover, it is shown that the layers are almost completely correlated over the sample thickness. The thickness fluctuations along the growth direction are estimated from the analysis of the large-angle (004) reflection, and the effective MnTe profile is also checked by dynamical simulation. It is shown that the small- and large-angle results are in good agreement. The MnTe profile width deduced from x-ray reflectivity is slightly overestimated due to the large integration area of this technique. An estimation of the local MnTe profile is given. © 2000 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1113-1115 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown by atomic layer epitaxy CdTe/MnTe tilted and serpentine superlattices. These heterostructures are formed by depositing in the step-flow growth mode fractional monolayer superlattices (CdTe)m(MnTe)n, with p=m+n∼1, onto 2 °A and 2 °B Cd0.95Zn0.05Te vicinal substrates. Transmission electron microscopy images reveal a good in-plane CdTe/MnTe separation and a uniform short-range superlattice period. The very existence of those superlattices imply that Te-based vicinal surfaces present a regular array of monomolecular steps, with no important step meandering and no step bunching. © 1997 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2966-2972 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A photothermal microscope that provides micrometer lateral and submicrometer depth resolution was designed. Thermal conductivity measurements with modulation frequencies up to 12 MHz on single grains in polycrystalline diamond demonstrate its lateral resolution power even for a highly conducting material. Measured conductivities strongly depend on the averaged volume and values up to 2200 W/mK are found in the high frequency limit where the properties inside a grain are sampled. The capability of the instrument to measure thermal parameters on thin films is demonstrated for gold films evaporated on quartz with a thickness ranging from 20 to 1500 nm. Measurements reveal a strong thickness dependence for both thin film conductivity and the contact resistance between film and substrate. Thermal conductivity decreases monotonically from 230 to 30 W/mK whereas the contact resistance rises from 2×10−7 to 8×10−6 m2K/W with decreasing film thickness. © 1997 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2013-2018 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermoreflectance technique is applied for imaging electric current distributions and thermal transfer in a temperature reference resistor heated by an alternating current. High-frequency scans (30 kHz) allow imaging of the current density distribution in conducting strips of the resistor while scans of amplitude and phase of the surface temperature variation at lower frequencies reveal plane, cylindrical, and spherical thermal waves. We investigate wave dimensionality as a function of heating geometry and thermal length, and present a simple method allowing a quantitative thermal analysis by exploiting the phase profile of cylindrical thermal waves. © 1996 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5266-5269 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple dispersion equation for surface thermal waves propagating along a solid surface covered with a thin film of higher thermal conductivity is presented. It is shown to describe well phase measurements with a photothermal microscope carried out on metal films on glass substrates. © 1995 American Institute of Physics.
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  • 6
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Line mixing effects are studied in the v3 band of CH4 perturbed by Ar and He at room temperature. Experiments have been made in the 2800–3200 cm−1 spectral region using four different setups. They cover a wide range of total densities, including low (0.25–2 atm), medium (25–100 atm), and high (200–1000 atm) pressure conditions. Analysis of the spectra demonstrates that the spectral shapes (of the band, the Q branch, the P and R manifolds,...) are significantly influenced by line mixing. The theoretical approach proposed in the preceding paper is used in order to model and analyze these effects. As done previously, semiclassical state-to-state rates are used together with a few empirical constants. Comparisons between measurements and spectra computed with and without the inclusion of line mixing are made. They prove the quality of the approach which satisfactorily accounts for the effects of pressure and of rotational quantum numbers on the spectral shape. It is shown that collisions with He and Ar lead to different line-coupling schemes (e.g., more coupling within the branches and less between branches) and hence to different shapes. The influence of line coupling between different branches and manifolds is evidenced and studied using high pressure spectra and absorption in the band wings. © 1999 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 1959-1968 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A model based on the energy corrected sudden approximation is used in order to account for line-mixing effects in N2O Q branches of Σ↔Π bands. The performance of this theoretical approach is demonstrated by comparisons with many (about 70) N2O–N2 and N2O–O2 laboratory spectra recorded in the 5 and 17 μm regions by three instrument setups; the Q branches of the 2ν20e–ν21f (near 579.3 cm−1), ν2 (near 588.8 cm−1), and ν2+ν3 (near 2798.3 cm−1) bands are investigated for different pressures (0.1–2.0 atm) and temperatures (200–300 K). The model is used to generate a set of line-mixing parameters for the calculation of the absorption by the ν2 Q branch under atmospheric conditions. These data are tested by comparisons between computed stratospheric emissions and values measured using a balloon-borne high resolution Fourier transform instrument. The results confirm the need to account for the effects of line mixing and demonstrate the capability of the model to represent the N2O absorption in a region which can be used for the retrieval of N2O5 mixing ratios. © 1999 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6684-6690 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Two Q branches of N2O near 579.3 and 2798 cm−1 belonging to the 2ν20e−ν21f and ν2+ν3 bands, respectively, of Σ←Π and Π←Σ symmetry, have been studied for He and N2 perturbers at pressures ranging from 0.1 to 2 atm, using a tunable diode laser and a difference-frequency laser spectrometer. To interpret the line-mixing effects in these spectra, we have applied a model based on the energy corrected sudden approximation whose parameters have been only derived from line-broadening data for N2O–He and also from the measured absorption by the Q branches for N2O–N2. This model provides a satisfactory agreement with experimental band shapes, whatever the band, the perturber and the pressure considered. Significantly larger line-mixing effects are shown for N2O–He with respect to N2O–N2. Finally, the assumption made in the calculations to treat separately the couplings in the even and odd j levels appears to have a negligible influence on the resulting band shapes. © 1998 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4889-4897 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The x-ray standing wave method is used in correlation with reflection high-energy electron diffraction and scanning tunneling microscopy to investigate the crystallographic features of MnTe monolayers inserted in CdTe (001). Either conventional molecular beam epitaxy or atomic layer epitaxy were employed for the formation of the CdTe starting surface, the deposition of the MnTe fractional monolayer, and its encapsulation by CdTe. Significant differences concerning the ratio of Mn atoms involved in MnTe clusters to those incorporated as part of a CdMnTe alloy are observed between the samples. Those differences are due to differing CdTe starting surface roughness. © 2000 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1951-1957 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed large and small angle x-ray scattering measurements on CdTe/MgTe superlattices. The individual thicknesses of the CdTe and MgTe layers, together with the period dispersion and the crystallographic quality of the stacking, were extracted from large-angle x-ray diffraction. The Fresnel optical method and the distorted wave Born approximation were used to analyze the small angle x-ray scattering data. Specular reflectivity shows that the interface roughness is quite large for the two CdTe/MgTe superlattices grown either by conventional molecular beam epitaxy or by atomic layer epitaxy with however in the latter case a strong asymmetry between the direct and inverted interfaces. The effective MgTe concentration is determined from the refractive index. A model of correlated interface profiles is successfully used to simulate the diffuse scattering, and to gain access to the lateral correlation length of the roughness (Λ(parallel)=1500±750 Å for both samples); moreover, we demonstrate that the layers are almost completely correlated over the sample thickness in the growth direction. © 1999 American Institute of Physics.
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