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1 Sep 1998

Volume 84, Issue 5, pp. 2371-2982

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The influence of “starving plasma” regime on carbon content and bonds in a-Si1−xCx:H thin films

I. Pereyra, M. N. P. Carreño, M. H. Tabacniks, R. J. Prado, and M. C. A. Fantini

J. Appl. Phys. 84, 2371 (1998); http://dx.doi.org/10.1063/1.368436 (9 pages) | Cited 17 times

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Differences on carbon content and chemical bonds in a-Si1−xCx:H were observed and analyzed in carbon rich and silicon rich films, deposited by plasma enhanced chemical vapor deposition from mixtures of silane and methane. The influence of the radio frequency low power density regime on the film’s properties was investigated. The content of Si, C, and H in the solid phase was obtained by Rutherford back scattering and forward recoil spectrometry. The bondings were analyzed by Fourier transform infrared spectroscopy. Quantitative analysis on the film’s chemical composition was performed combining the vibrational spectra with the stoichiometry data. The results showed that under “silane starving plasma” conditions, a carbon content as high as 70 at. % is achieved and the main carbon bonds are tetragonal C–H, C–H2, and Si–C. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Gc Amorphous semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
61.43.Dq Amorphous semiconductors, metals, and alloys
78.35.+c Brillouin and Rayleigh scattering; other light scattering
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
63.50.-x Vibrational states in disordered systems

Two-photon absorption and nonlinear refraction of lanthanum sulfide-gallium sulfide glasses

Zhong Hua Zhou, Tadanori Hashimoto, Hiroyuki Nasu, and Kanichi Kamiya

J. Appl. Phys. 84, 2380 (1998); http://dx.doi.org/10.1063/1.368363 (5 pages) | Cited 3 times

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The two-photon absorption coefficient (β) and nonlinear refractive index (γ) of the binary La2S3–Ga2S3 and ternary MS–La2S3–Ga2S3 (MS=Ag2S and Na2S) glasses were measured at 532 nm by the Z-scan method. The β of the glasses was ∼ 40 cm GW−1 and nearly unchanged with La2S3 content in the binary glasses, while it increased, or decreased with the substitution of Ag2S, or Na2S, respectively, for La2S3 in the ternary glasses. The γ of the glasses increased, with the rising La2S3 content in the binary glasses, and increased, or decreased with the addition of Ag2S, or Na2S, respectively, in the ternary glasses. The results were compared with the third-order nonlinear optical properties measured by third harmonic generation and discussed on the basis of their linear optical properties. © 1998 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Ce Glasses, quartz
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Universal power optimized work for reciprocating internally reversible Stirling-like heat engine cycles with regeneration and linear external heat transfer

David A. Blank

J. Appl. Phys. 84, 2385 (1998); http://dx.doi.org/10.1063/1.368364 (8 pages) | Cited 8 times

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When bounded by two infinite thermal reservoirs, the theory of irreversible thermodynamics for reciprocating externally irreversible cycles yields to an optimum efficiency at maximum power output of η = 1−(TL/TH)0.5 for internally reversible Stirling-like cycles using regeneration and linear heat transfer modes is in contrast to the upper limit for Stirling cycles of η = 1−(TL/TH) obtained from classical thermodynamics. This optimum behavior is, however, only based on cycle temperature bounds. For reciprocating cycles one must go a step further and minimize cycle time. While executing this new step for finite thermal reservoirs, it was discovered that, for the general family of reciprocating Stirling-like cycles, the finite-time optimum work output (Wopt) at maximum power is less than (and in the limit of ideal regeneration, infinite reservoirs and of no internal irreversibility, is equal to) exactly one-half of the work of the externally reversible cycle operating at maximum thermal efficiency (Carnot work, Wrev) between the same temperature limits (i.e., Wopt ⩽ ½Wrev). To accomplish this the analysis goes beyond earlier works to use time symmetry to better optimize overall cycle power. Because this procedure results in the concurrent employment of the first and second laws of thermodynamics, it ensures optimal allocation of thermal conductances at the hot and cold ends while simultaneously achieving both minimization of internal entropy generation and maximization of specific cycle work for a given set of operating temperatures. Based on linear heat transfer laws, this expression for optimum work is shown to be independent of heat conductances. Finally, the analysis establishes that the maximum power attainable for a Stirling-like reciprocating cycle operating between two temperature bounds is always less than (and in the limit of power optimized Carnot conditions, equal to) one-half of that obtained for the continuous counterpart of the same cycle operating between the same temperature bounds. © 1998 American Institute of Physics.
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05.70.Ln Nonequilibrium and irreversible thermodynamics
07.20.Pe Heat engines; heat pumps; heat pipes
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