ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    Contribution of defects to electronic, structural, and thermodynamic properties of amorphous silicon (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7266-7286 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The structure of pure, nonhydrogenated amorphous silicon (a-Si) was modified by means of ion implantation, furnace annealing, and pulsed laser annealing. Defects in a-Si were probed by measuring the photocarrier lifetime τ at low carrier densities (1018/cm3) with subpicosecond resolution using pump-probe reflectivity measurements. The average cross section of defect-related midgap states for free-carrier capture is found to be 6×10−16 cm2. In addition, the average bond-angle distortion Δθ in a-Si was derived from Raman spectroscopy. Annealing as-implanted a-Si for 1 h at T≤500 °C induces defect annihilation as well as network relaxation. In contrast, 32 ns pulsed laser heating of a-Si just below the melting threshold leads to relaxation of Δθ without significant defect annihilation. This annealing behavior can be understood on the basis of defect diffusion kinetics. Implanting fully relaxed a-Si with 1 MeV B+, Si+, and Xe+ up to damage levels of 0.004 displacements per atom raises the defect density without affecting Δθ. Only after the defect density has saturated at higher damage levels is Δθ returned to the as-implanted level. The electronic density of states of a-Si is determined using optical-absorption spectroscopy, yielding Nsat≈0.5 at. % for the saturation defect density in a-Si at room temperature. Electron paramagnetic resonance shows that a minor fraction (0.02 at. %) of these defects is spin active. The response of c-Si and relaxed a-Si to implantation damage is comparable, suggesting that the defect populations in both materials are similar. Comparing carrier lifetime measurements and Raman spectroscopy for the various experimental treatments demonstrates that there is no unique correlation between the defect density and Δθ in a-Si. Assuming that defects and Δθ have independent enthalpic contributions, the Gibbs free energy of various structural states of a-Si is calculated. These calculations indicate that the melting temperature of a-Si may vary from 1010 to 1490 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.356662
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    facet.materialart.
    Unbekannt
    The effect of residual gas scattering on Ga ion beam patterning of graphene (2015)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2015-11-24
    Beschreibung: The patterning of graphene by a 30 kV Ga + focused ion beam (FIB) is studied by in-situ and ex-situ Raman spectroscopy. It is found that the graphene surrounding the patterned target area can be damaged at remarkably large distances of more than 10  μ m. We show that scattering of the Ga ions in the residual gas of the vacuum system is the main cause of the large range of lateral damage, as the size and shape of the tail of the ion beam were strongly dependent on the system background pressure. The range of the damage was therefore greatly reduced by working at low pressures and limiting the total amount of ions used. This makes FIB patterning a feasible alternative to electron beam lithography as long as residual gas scattering is taken into account.
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    AKTUELLE ARTIKEL
  • 3
    facet.materialart.
    Unbekannt
    Wavelet analysis methods for radiography of multidimensional growth of planar mixing layers (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-07-07
    Beschreibung: The counter-propagating shear campaign is examining instability growth and its transition to turbulence in the high-energy-density physics regime using a laser-driven counter-propagating flow platform. In these experiments, we observe consistent complex break-up of and structure growth in a tracer layer placed at the shear flow interface during the instability growth phase. We present a wavelet-transform based analysis technique capable of characterizing the scale- and directionality-resolved average intensity perturbations in static radiographs of the experiment. This technique uses the complete spatial information available in each radiograph to describe the structure evolution. We designed this analysis technique to generate a two-dimensional power spectrum for each radiograph from which we can recover information about structure widths, amplitudes, and orientations. The evolution of the distribution of power in the spectra for an experimental series is a potential metric for quantifying the structure size evolution as well as a system’s evolution towards isotropy.
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Publiziert von American Institute of Physics (AIP)
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    AKTUELLE ARTIKEL
  • 4
    facet.materialart.
    Unbekannt
    A generalization of the Drude-Smith formula for magneto-optical conductivities in Faraday geometry (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-07-01
    Beschreibung: In this study, we generalize the impulse response approach and Poisson statistics proposed by Smith [Phys. Rev. B 64 , 155106 (2001)] to evaluate the longitudinal and transverse magneto-optical conductivities in an electron gas system in Faraday geometry. Comparing with the standard Drude model, the coefficients a n are introduced in the Drude-Smith formula to describe the backscattering or localization effect for the n th electronic scattering event. Such a formula can also be applied to study the elements of the dielectric function matrix in the presence of magnetic and radiation fields in electron gas systems. This theoretical work is primely motivated by recent experimental activities in measuring the real and imaginary parts of longitudinal and transverse magneto-optical conductivities in condensed matter materials and electronic devices using terahertz time-domain spectroscopy. We believe that the results obtained from this study can provide an appropriate theoretical tool in reproducing the experimental findings and in fitting with experimental data to determine the important sample and material parameters.
    Print ISSN: 0021-8979
    Digitale ISSN: 1089-7550
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    AKTUELLE ARTIKEL
  • 5
    facet.materialart.
    Unbekannt
    The Shock/Shear platform for planar radiation-hydrodynamics experiments on the National Ignition Facilitya) (2015)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2015-04-18
    Beschreibung: An indirectly-driven shock tube experiment fielded on the National Ignition Facility (NIF) was used to create a high-energy-density hydrodynamics platform at unprecedented scale. Scaling up a shear-induced mixing experiment previously fielded at OMEGA, the NIF shear platform drives 130  μ m/ns shocks into a CH foam-filled shock tube (∼ 60 mg/cc) with interior dimensions of 1.5 mm diameter and 5 mm length. The pulse-shaping capabilities of the NIF are used to extend the drive for 〉10 ns, and the large interior tube volumes are used to isolate physics-altering edge effects from the region of interest. The scaling of the experiment to the NIF allows for considerable improvement in maximum driving time of hydrodynamics, in fidelity of physics under examination, and in diagnostic clarity. Details of the experimental platform and post-shot simulations used in the analysis of the platform-qualifying data are presented. Hydrodynamic scaling is used to compare shear data from OMEGA with that from NIF, suggesting a possible change in the dimensionality of the instability at late times from one platform to the other.
    Print ISSN: 1070-664X
    Digitale ISSN: 1089-7674
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    AKTUELLE ARTIKEL
  • 6
    facet.materialart.
    Unbekannt
    Modifying mixing and instability growth through the adjustment of initial conditions in a high-energy-density counter-propagating shear experiment on OMEGA (2015)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2015-06-25
    Beschreibung: Counter-propagating shear experiments conducted at the OMEGA Laser Facility have been evaluating the effect of target initial conditions, specifically the characteristics of a tracer foil located at the shear boundary, on Kelvin-Helmholtz instability evolution and experiment transition toward nonlinearity and turbulence in the high-energy-density (HED) regime. Experiments are focused on both identifying and uncoupling the dependence of the model initial turbulent length scale in variable-density turbulence models of k- ϵ type on competing physical instability seed lengths as well as developing a path toward fully developed turbulent HED experiments. We present results from a series of experiments controllably and independently varying two initial types of scale lengths in the experiment: the thickness and surface roughness (surface perturbation scale spectrum) of a tracer layer at the shear interface. We show that decreasing the layer thickness and increasing the surface roughness both have the ability to increase the relative mixing in the system, and thus theoretically decrease the time required to begin transitioning to turbulence in the system. We also show that we can connect a change in observed mix width growth due to increased foil surface roughness to an analytically predicted change in model initial turbulent scale lengths.
    Print ISSN: 1070-664X
    Digitale ISSN: 1089-7674
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    AKTUELLE ARTIKEL
  • 7
    facet.materialart.
    Unbekannt
    Development of a Big Area BackLighter for high energy density experiments (2014)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2014-09-05
    Beschreibung: A very large area (7.5 mm 2 ) laser-driven x-ray backlighter, termed the Big Area BackLighter (BABL) has been developed for the National Ignition Facility (NIF) to support high energy density experiments. The BABL provides an alternative to Pinhole-Apertured point-projection Backlighting (PABL) for a large field of view. This bypasses the challenges for PABL in the equatorial plane of the NIF target chamber where space is limited because of the unconverted laser light that threatens the diagnostic aperture, the backlighter foil, and the pinhole substrate. A transmission experiment using 132 kJ of NIF laser energy at a maximum intensity of 8.52 × 10 14 W/cm 2 illuminating the BABL demonstrated good conversion efficiency of 〉3.5% into K-shell emission producing ∼4.6 kJ of high energy x rays, while yielding high contrast images with a highly uniform background that agree well with 2D simulated spectra and spatial profiles.
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Publiziert von American Institute of Physics (AIP)
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    AKTUELLE ARTIKEL
  • 8
    facet.materialart.
    Unbekannt
    Combined optical sizing and acoustical characterization of single freely-floating microbubbles (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-12-08
    Beschreibung: In this study we present a combined optical sizing and acoustical characterization technique for the study of the dynamics of single freely-floating ultrasound contrast agent microbubbles exposed to long burst ultrasound excitations up to the milliseconds range. A co-axial flow device was used to position individual microbubbles on a streamline within the confocal region of three ultrasound transducers and a high-resolution microscope objective. Bright-field images of microbubbles passing through the confocal region were captured using a high-speed camera synchronized to the acoustical data acquisition to assess the microbubble response to a 1-MHz ultrasound burst. Nonlinear bubble vibrations were identified at a driving pressure as low as 50 kPa. The results demonstrate good agreement with numerical simulations based on the shell-buckling model proposed by Marmottant et al . [J. Acoust. Soc. Am. 118 , 3499–3505 (2005)]. The system demonstrates the potential for a high-throughput in vitro characterization of individual microbubbles.
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    AKTUELLE ARTIKEL
  • 9
    Digitale Medien
    Digitale Medien
    Study of mechanical alloying of Sm and Fe : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5805-5807 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Mechanical alloying of Sm and Fe with the composition of SmFe3 was studied using x-ray-diffraction (XRD), Mössbauer, and magnetization measurements. Data taken as a function of milling time for up to 20 h show significant changes occurring during ball milling. The XRD studies show that the initial crystalline Bragg reflections changed to a broad maximum, which is attributed to the formation of an amorphous phase. The initial six-line pattern in the Mössbauer spectrum, characteristic of magnetic ordering, changed to a broad singlet, characteristic of a nonmagnetic material. Magnetization measurements revealed that the coercive field was at its maximum after 5 h of milling and decreased sharply as the milling time increased. The remanent magnetization was at its maximum between 5 and 10 h of milling. The final product of the ball milling, which exhibited the characteristics of an amorphous paramagnetic material in its XRD and Mössbauer spectrum, was studied after heat treatment. The XRD and the Mössbauer spectra of the heat treated alloy show that substantial changes occurred during heat treatment in that sharp Bragg reflections, characteristic of crystalline materials, reappear and the alloy changed from a paramagnetic to a ferromagnetic state. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.364674
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 10
    Digitale Medien
    Digitale Medien
    Thermal stability of diamondlike carbon films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3068-3075 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: IR and UV-VIS optical spectroscopy have been used to study the transformations of the properties of diamondlike carbon films following isothermal anneals from Ta=300 to 650 °C. Several processes due to the annealing have been observed: (1) the increase of the absorption due to vibrations of unsaturated bonds of C(sp2) atoms at ∼1600 cm−1 for Ta≥350 °C, (2) the decrease of the absorption due to C(sp3)–H bonds at Ta≥350 °C, and (3) the reduction of the optical energy gap. Analysis of the kinetics has shown that the dehydrogenation of the alloys and the formation of unsaturated bonds may proceed independently. The reduction of the energy gap is related to the formation of C(sp2) atoms with unsaturated bonding which occurs mostly in hydrogen-free regions. Intensive graphitization of the films occurs above Ta=650 °C. Transformations of C–H bonds are proposed to occur via fast rearrangement in stressed regions leading to formation of new C(sp2)–H bonds and formation of methane molecules as the most important product of the anneals inside the polymeric highly hydrogenated regions in the alloys. It appears that both bond removal and reordering have taken place as a result of annealing. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.363167
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...