Optical properties of amorphous silicon nitride films.
Item
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Title
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Optical properties of amorphous silicon nitride films.
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Identifier
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AAI9130393
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identifier
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9130393
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Creator
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Yin, Zhiping.
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Contributor
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Adviser: F. W. Smith
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Date
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1991
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Optics | Physics, Condensed Matter
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Abstract
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The optical dielectric function {dollar}\epsilon{dollar} (1.5 to 6.25 eV), infrared (IR) absorption (400-4000 cm{dollar}\sp{lcub}-1{rcub}{dollar}), and film density have been measured for a series of a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}{dollar} films prepared by plasma enhanced CVD (PECVD). From a detailed analysis of the infrared absorption bands, dielectric functions, and density results, the concentrations of Si-H, N-H, Si-Si, and Si-N bonds and of Si, N, and H atoms have been obtained for the films studied. The effects of substrate temperature T{dollar}\sb{lcub}\rm s{rcub}{dollar}, reactant ratio R, and power density on the film composition, density and dielectric function have been studied. The temperature-dependence and annealing behavior of the IR absorption in a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}{dollar} films have been observed from 77{dollar}\sp\circ{dollar}K up to 350{dollar}\sp\circ{dollar}C. The effects of temperature on hydrogen bonding, O-H{dollar}\cdots{dollar}O, have been observed in a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}O{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}{dollar} films. No strong effect of temperature on hydrogen bonding, N-H{dollar}\cdots{dollar}N, in a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}{dollar} has been observed. It has been found that the N-rich diimidelike films prepared here have very low porosities and are thermally stable up to 700{dollar}\sp\circ{dollar}C.;A microstructural model based on Si-centered tetrahedra is developed for a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}{dollar} alloys. The dependence of the optical dielectric function {dollar}\epsilon{dollar} of the a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}{dollar} alloys on stoichiometry ( (N) / (Si) ratio) and hydrogen content has been determined for (1) Si-rich a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm 1-x{rcub}{dollar} alloys (containing no hydrogen); (2) N-rich a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm y-z{rcub}{dollar}(NH){dollar}\sb{lcub}\rm z{rcub}{dollar} alloys. By using the Si-centered tetrahedron model as combined with the Bruggemenn effective-medium approximation (EMA) analysis, Si-Si bond concentrations in the a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}{dollar} films can be obtained reliably since Si-Si weak bonds have a strong effect on the dielectric function {dollar}\epsilon{dollar}.;A free energy model (FEM) for bonding in amorphous covalent alloys is developed and applied to the ternary a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}{dollar} alloy system. The Gibbs free energy of mixing G{dollar}\sb{lcub}\rm M{rcub}{dollar} = H{dollar}\sb{lcub}\rm M{rcub}{dollar} -TS{dollar}\sb{lcub}\rm M{rcub}{dollar} is obtained with use of the quasichemical approach to the thermodynamics of regular solutions, where H{dollar}\sb{lcub}\rm M{rcub}{dollar} is enthalpy of mixing and S{dollar}\sb{lcub}\rm M{rcub}{dollar} is the entropy of mixing. Chemical ordering (CO) in these alloys is shown to correspond to the preference for Si-N and Si-H bonds at the expense of Si-Si and N-H bonds. Using the FEM, the bond concentration fractions can be predicted.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
