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15 Sep 1998

Volume 84, Issue 6, pp. 2989-3428

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Light scattering and enhanced optical absorption in hot wire microcrystalline silicon

F. Diehl, B. Schröder, and H. Oechsner

J. Appl. Phys. 84, 3416 (1998); http://dx.doi.org/10.1063/1.368501 (3 pages) | Cited 2 times

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It is attempted to clarify the origin of the enhanced optical absorption in hot wire microcrystalline silicon (hw-μc-Si:H) which is not yet fully understood. We investigated the influence of elastic light scattering on the enhanced optical absorption of hw-μc-Si:H by means of an Ulbricht sphere and angular resolved scattering measurements, respectively. The experiments clearly revealed that elastic light scattering is not mainly responsible for the enhanced optical absorption in hw-μc-Si:H compared to that in monocrystalline material. They confirm the absorption enhancement to be a bulk effect which is determined by the structural properties of the material and the hydrogen incorporation into the samples. With regard to the origin of the absorption enhancement we refer to an absorption model for hw-μc-Si:H being briefly outlined. © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.35.+c Brillouin and Rayleigh scattering; other light scattering
72.80.Cw Elemental semiconductors

Soft x-ray emission of laser-produced plasmas using a low-debris cryogenic nitrogen target

R. Lebert, G. Schriever, T. Wilhein, and B. Niemann

J. Appl. Phys. 84, 3419 (1998); http://dx.doi.org/10.1063/1.368502 (3 pages) | Cited 9 times

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Laser-produced nitrogen plasmas (LPPs) are intense narrow-band emitters in the “water window” spectral range which is suited for x-ray microscopy of biological samples. Frozen gases as target materials are predicted to have low debris precipitated onto laser or x-ray optics arranged inside the vacuum chamber. Gaseous nitrogen is frozen onto a metal surface at a temperature of 16 K. The solid nitrogen is illuminated with nanosecond pulsed laser radiation with intensities of 1.3×1013 W/cm2 and the emission characteristics of laser-produced nitrogen plasmas are investigated with a calibrated imaging spectrograph. The x-ray emission in the water window region is compared to the radiation of a LPP with a solid boron nitride target at the same laser parameters. © 1998 American Institute of Physics.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.La X-ray and γ-ray measurements

Simultaneous determination of the compositions and thicknesses of a multilayer film using spectroreflectometry

David W. Weyburne and Qing S. Paduano

J. Appl. Phys. 84, 3422 (1998); http://dx.doi.org/10.1063/1.368503 (3 pages)

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In the growth of III–V epitaxial layers, spectroreflectometry is a fast, convenient method for measuring layer thickness. The experimentally measured optical thickness is the product of the composition-dependent refractive index and the layer thickness. In the past, the thickness of a ternary layer was uniquely determined by fixing the composition using photoluminescence or x-ray measurements. In this article, we show that the decoupling can be accomplished by measuring and fitting the spectroreflectance in a wavelength range where there is significant variation of the refractive index, for example, near the semiconductor band gap. The technique is demonstrated by the simultaneous measurement of the compositions and thicknesses of multilayered AlGaAs/GaAs films incorporating up to three different AlGaAs compositions. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
07.60.Hv Refractometers and reflectometers
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Energy relaxation of hot electrons driven by intense terahertz fields in two-dimensional semiconductor systems

X. L. Lei and Y. Q. Chen

J. Appl. Phys. 84, 3425 (1998); http://dx.doi.org/10.1063/1.368504 (3 pages) | Cited 1 time

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We examine the frequency dependence of the energy relaxation of hot electrons under the influence of an intense oscillating electric field of terahertz frequency. The calculated energy-loss rates in a GaAs/AlGaAs heterojunction and two GaAs-based quantum wells exhibit a frequency behavior quite different from that of the widely used Kogan formula. Their ratio shows an unexpected peak at around 0.5–0.6 THz, with a height about 3–10 times of its low-frequency value. This remarkable resonance is a unique indication of the role of the Doppler shift of the phonon frequency. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.30.+q High-frequency effects; plasma effects
73.50.Mx High-frequency effects; plasma effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
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