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  • 1
    Digitale Medien
    Digitale Medien
    Structure of interfaces in a-SiB: H/a-SiNx@B: H superlattices (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 778-785 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present experimental results on the atomic structure of the interfaces between a-Si:H and a-SiNx:H layers obtained by analyzing the intensity of the Raman lines from zone-folded acoustic phonons and of the peaks of x-ray diffraction at grazing angles. We determine the width of these interfaces and their stability under thermal annealing in temperatures below the crystallization temperature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347364
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  • 2
    Digitale Medien
    Digitale Medien
    Efficient energy upconversion emission in Tm3+/Yb3+-codoped TeO2-based optical glasses excited at 1.064 μm (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6550-6552 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Efficient energy upconversion of cw radiation at 1.064 μm into blue, red, and near infrared emission in Tm3+-doped Yb3+-sensitized 60TeO2-10GeO2-10K2O-10Li2O-10Nb2O5 glasses is reported. Intense blue upconversion luminescence at 485 nm corresponding to the Tm3+ 1G4→3H6 transition with a measured absolute power of 0.1 μW for 800 mW excitation power at room temperature is observed. The experimental results also revealed a sevenfold enhancement in the upconversion efficiency when the sample was heated from room temperature to 235 °C yielding 0.7 μW of blue absolute fluorescence power for 800 mW pump power. High brightness emission around 800 nm (3F4→3H6) in addition to a less intense 655 nm (1G4→3H4 and 3F2,3→3H6) fluorescence is also recorded. The energy upconversion excitation mechanism for thulium emitting levels is assigned to multiphonon-assisted anti-Stokes excitation of the ytterbium-sensitizer followed by multiphonon-assisted sequential energy-transfer processes. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1413489
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  • 3
    Digitale Medien
    Digitale Medien
    Laser interference structuring of a-Ge films on GaAs (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2916-2920 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated the laser interference crystallization (LIC) of amorphous germanium films on (100)-oriented GaAs substrates using nanosecond laser pulses. We demonstrate that LIC can produce periodic arrays of epitaxially crystallized Ge lines on GaAs with submicrometer widths. The gratings display a surface undulation with faceted surfaces, which depends on laser fluency. The undulation is attributed to the lateral solidification process induced by the temperature gradients created during the LIC process. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1448674
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  • 4
    Digitale Medien
    Digitale Medien
    Study of structural changes in amorphous germanium–nitrogen alloys by optical techniques (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 433-438 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Thin films of amorphous germanium–nitrogen (a-GeN) alloys prepared by the rf sputtering deposition technique have been studied by Raman scattering spectroscopy. The nitrogen content of the samples varies between zero and ≈3×1022 atoms cm−3, as determined from nuclear reaction analysis data. Modifications of the structural characteristics of the Ge–N alloys, probed through their phonon density, were investigated as a function of the nitrogen concentration. In addition to an increase of the network's topological disorder, nitrogen is responsible, at relatively high concentrations, for a structural transition in the a-Ge host. The optical and electronic characterization of the samples confirm these changes which are highly dependent on the nitrogen concentration. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360849
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  • 5
    Digitale Medien
    Digitale Medien
    Short-pulse laser-induced crystallization of intrinsic and hydrogenated amorphous germanium thin films (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 5159-5166 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on the laser crystallization of intrinsic (a-Ge) and hydrogenated (a-Ge:H) amorphous germanium thin films using short, i.e., ns range, laser pulses. The influence of hydrogen on the phase transitions was investigated by monitoring the reflectance of the sample during laser irradiation. We determined the thresholds for melting (36 mJ/cm2) and for surface damage (66 mJ/cm2) of the a-Ge film. In a-Ge:H, hydrogen effuses on a short time scale (10 ns) upon laser irradiation. The effusion leads to the formation of a lifted-off (100 nm thick) crystalline Ge membrane, leaving behind a rough and incompletely crystallized surface. In a-Ge, on the other hand, no surface disruption is observed. The Raman spectra of hydrogenated samples are dominated by stress effects, while those corresponding to non-hydrogenated samples are dominated by crystallite size distribution effects. We also conclude that laser-induced annealing, carried out by applying several pulses with increasing intensity, can be used as a tool for the crystallization of a-Ge:H samples without hydrogen-induced surface damage. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.366320
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  • 6
    Digitale Medien
    Digitale Medien
    Epitaxial pulsed laser crystallization of amorphous germanium on GaAs (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2575-2581 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated the crystallization of amorphous germanium films on GaAs crystals using nanosecond laser pulses. The structure and composition of the crystallized layers is dominated by nonequilibrium effects induced by the fast cooling process following laser irradiation. Perfect epitaxial films are obtained for fluencies that completely melt the Ge film, but not the substrate. For higher fluencies, partial melting of the substrate leads to the formation of a (GaAs)1−xGe2x epitaxial alloy with a graded composition profile at the interface with the substrate. Since Ge and GaAs are thermodynamically immiscible in the solid phase, the formation of the alloy is attributed to the suppression of phase separation during the fast cooling process. Lower laser fluencies lead to polycrystalline layers with a patterned surface structure. The latter is attributed to the freeze-in of instabilities in the melt during the fast solidification process. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1390312
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  • 7
    Digitale Medien
    Digitale Medien
    Stability of hydrogenated amorphous silicon deposited at high temperatures with a remote hydrogen plasma (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1443-1445 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: It is demonstrated that the stability of hydrogenated amorphous silicon (a-Si:H) is improved by deposition under the combined conditions of high substrate temperature (e.g., TD=400 °C) and high hydrogen dilution, as are readily achieved in a remote hydrogen plasma reactor. In comparison with optimized films from conventional rf glow discharge deposition (e.g., silane, 230 °C, 2 W), undoped high TD films possess a lower midgap defect density, the dark dc conductivity in n-type (phosphorus-doped) films displays higher equilibration temperatures and longer relaxation times at a given temperature with an activation energy of 1.0 eV, and undoped high TD films have a lower saturated density of light-induced defects. It is proposed that the ability to achieve the improved stability is a consequence of two effects: (1) the use of hydrogen dilution during deposition to maintain the hydrogen concentration in the film near 10 at. % even at 400 °C and (2) the possibility that at high TD's the hydrogen is more stably incorporated in the random network and/or that the density of weak Si—Si bonds is smaller.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105282
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  • 8
    Digitale Medien
    Digitale Medien
    Lateral structuring of silicon thin films by interference crystallization (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3148-3150 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Laterally structured microcrystalline silicon in the submicron range has been produced from amorphous silicon thin films by transient holography using a high-energy pulse laser. The energy density along the lines of the transient optical grid is sufficient to induce crystallization at the intensity maxima. Large area laterally structured microcrystalline silicon has been produced by selectively etching the amorphous phase with simultaneous growth of μc-Si:H in a hydrogen-silane plasma.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.111347
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  • 9
    Digitale Medien
    Digitale Medien
    Optical temperature sensing using upconversion fluorescence emission in Er3+/Yb3+-codoped chalcogenide glass (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 578-580 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Optical temperature sensing using upconversion fluorescence emission in Er3+/Yb3+-codoped Ga2S3:La2O3 chalcogenide glass excited at 1.06 μm is reported. Temperature measurements in the region of 20–225 °C with a resolution of approximately 0.5 °C using excitation powers of a few tens of milliwatts were obtained. The temperature sensing mechanism is independent of variations in the excitation intensity, possible fluctuations of transmission, and utilizes a simple signal detection and processing system. The results also revealed that the glass host material plays an important role in the performance of the sensing system. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.121861
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  • 10
    Digitale Medien
    Digitale Medien
    Laser crystallization and structuring of amorphous germanium (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3570-3572 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The short-pulse laser crystallization and interference structuring of amorphous germanium films were investigated by time resolved reflection measurements and Raman spectroscopy. We demonstrate that submicrometer crystalline structures with very sharp lateral interfaces can be produced by laser interference crystallization of nonhydrogenated samples. In hydrogenated films, on the other hand, the film surface disrupts upon laser exposure leading to the formation of a free-standing crystalline membrane. The Raman spectra of laser crystallized germanium display effects of finite crystallite size and stress. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.119236
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