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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3708-3712 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A possible generation scheme for growing coherent plasma oscillations (plasma instability) is presented. Specific quantum well structures, where a sufficient population inversion can be maintained in the carrier distribution by appropriate injection–extraction configurations, form the basis of this scheme. Self-consistent random phase approximation calculations show that a population inversion, leading to a plasma instability, can occur in such structures. A comparison between the calculated and the observed differential conductance curves suggests that such quantum well structures could be designed as active regions for the generation of terahertz frequency radiation sources. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 461-463 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use real time, high sensitivity infrared reflectance spectroscopy to quantitatively study hydrogen incorporation during the growth of hydrogenated amorphous silicon by magnetron sputtering. For the range of deposition conditions studied (substrate temperature between 120 and 270 °C and H2 partial pressure between 0.1 and 1.0 mTorr, which result in film hydrogen content between 10 and 30 at. %), hydrogen incorporation reaches steady state for film thickness, d(approximately-greater-than)25 A(ring). Deviations from uniform growth for d〈25 A(ring) are attributed to plasma-substrate interactions due to energetic hydrogen implantation tens of angstroms beneath the growing surface and changes in the surface area during nucleation and coalescence.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 330-332 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report epitaxial growth of silicon on Si(100) at 230 °C by reactive dc magnetron sputter deposition. Growth is monitored with in situ multiwavelength ellipsometry to determine the film microstructure. Film crystallinity depends on the partial pressure of hydrogen during deposition, and the best film is obtained with 2 mTorr H2. The films are found to have a bulk density deficit of a few percent and a low-density layer at the film-substrate interface. The microstructure is confirmed by transmission electron microscopy measurements. Infrared absorption and thermal hydrogen evolution measurements indicate that a large amount of molecular hydrogen is present at the substrate interface. We discuss the possible roles of hydrogen and particle bombardment in promoting epitaxial growth.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use in situ spectroscopic ellipsometry to analyze the microstructure of the μc-Si:H/a-Si:H interface deposited by reactive magnetron sputtering of a Si target in (Ar+H2). We increase the hydrogen pressure to promote μc-Si:H formation and observe several effects. Initially, H penetrates ∼45 A(ring) into the a-Si:H substrate and increases its hydrogen content. Then ∼55 A(ring) of hydrogen-rich a-Si:H deposits. Finally, μc-Si:H nucleates on top of this ∼100 A(ring) thick, high H-content a-Si:H interface layer. As μc-Si:H grows, the thickness of the amorphous interface layer decreases by ∼40 A(ring); the void fraction in the μc-Si:H layer is always ≤15 vol %, ruling out the possibility that the a-Si:H is etched away. These results suggest that a-Si:H can be transformed into μc-Si:H in a subsurface region under appropriate conditions. © 1994 American Institue of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1685-1687 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Growing coherent plasma oscillations (plasma instability) can be generated in quantum well structures, where a sufficient population inversion is maintained in the carrier distribution by appropriate injection–extraction configurations. The collective response characteristics of such structures have been calculated. Such structures have been grown, and their radiation emission spectra observed. The experimental results are in agreement with the theoretical predictions. The emission maximum is in the terahertz frequency range, and occurs at an intersubband plasmon frequency. This shows that population inversion is achieved in these structures. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2018-06-16
    Description: Demonstration of coherent control and characterization of the control fidelity is important for the development of quantum architectures such as nuclear magnetic resonance (NMR). We introduce an experimental approach to realize universal quantum control, and benchmarking thereof, in zero-field NMR, an analog of conventional high-field NMR that features less-constrained spin dynamics. We design a composite pulse technique for both arbitrary one-spin rotations and a two-spin controlled-not (CNOT) gate in a heteronuclear two-spin system at zero field, which experimentally demonstrates universal quantum control in such a system. Moreover, using quantum information–inspired randomized benchmarking and partial quantum process tomography, we evaluate the quality of the control, achieving single-spin control for 13 C with an average fidelity of 0.9960(2) and two-spin control via a CNOT gate with a fidelity of 0.9877(2). Our method can also be extended to more general multispin heteronuclear systems at zero field. The realization of universal quantum control in zero-field NMR is important for quantum state/coherence preparation, pulse sequence design, and is an essential step toward applications to materials science, chemical analysis, and fundamental physics.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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