Diamond-like carbon alloy films based on carbon-nitrogen and hydrogen.
Item
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Title
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Diamond-like carbon alloy films based on carbon-nitrogen and hydrogen.
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Identifier
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AAI9807925
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identifier
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9807925
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Creator
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Efstathiadis, Haralabos.
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Contributor
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Adviser: F. W. Smith
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Date
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1997
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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, Condensed Matter | Chemistry, Organic | Engineering, Materials Science
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Abstract
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This thesis presents the results of a systematic study of the deposition and characterization of a series of amorphous hydrogenated carbon-nitrogen alloy films (a-C{dollar}\sb{lcub}\rm x{rcub}{dollar}N{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}){dollar} prepared via plasma-enhanced CVD from mixtures of ammonia and acetylene and from mixtures of nitrogen and acetylene. The effects of the ratio of reactants on the film composition, the optical constants, and the optical energy gap have been determined. It is found that the presence of nitrogen in the gas phase during deposition decreases the film deposition rate and that incorporation of nitrogen into the film is limited to N/C {dollar}\approx{dollar} 0.1. As the concentration of N in the film increases, the concentration of C also increases while the concentration of H decreases. No evidence for the theoretically-predicted C{dollar}\sb3{dollar}N{dollar}\sb4{dollar} compound was found. The addition of nitrogen into the film causes the index of refraction and the optical gap to decrease and leads to a redistribution of hydrogen between carbon and nitrogen. Hydrogen is preferentially bonded to nitrogen and there is evidence for N-H{dollar}{lcub}\cdots{rcub}{dollar}N hydrogen bonding in the films. The temperature dependencies of the infrared absorption of a-C{dollar}\sb{lcub}\rm x{rcub}{dollar}H{dollar}\sb{lcub}\rm y{rcub}{dollar} and a-C{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 also been studied from 77 K up to 700{dollar}\sp\circ{dollar}C. Film 'graphitization' is accomplished at approximately 650{dollar}\sp\circ{dollar}C.;The free energy model (FEM) previously developed for predicting the bonding in amorphous covalent alloys has been outlined here for the following alloys based on silicon: a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}C{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z,{rcub}{dollar} 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} with defects, a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}Ge{dollar}\sb{lcub}\rm y{rcub}{dollar}O{dollar}\sb{lcub}\rm z{rcub},{dollar} a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}Ge{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub},{dollar} a-Si{dollar}\sb{lcub}\rm x{rcub}{dollar}Ge{dollar}\sb{lcub}\rm y{rcub}{dollar}H{dollar}\sb{lcub}\rm z{rcub}{dollar} with defects and further developed and applied to the a-C{dollar}\sb{lcub}\rm x{rcub}{dollar}H{dollar}\sb{lcub}\rm y{rcub}{dollar} and a-C{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 importance of configurational entropy in determining the most stable state of these alloys is demonstrated. For the case of a-C{dollar}\sb{lcub}\rm x{rcub}{dollar}H{dollar}\sb{lcub}\rm y{rcub}{dollar} alloys predictions have been made for the distribution of bonds in tetrahedral C(sp{dollar}\sp3{dollar})- and planar C(sp{dollar}\sp2{dollar})=C(sp{dollar}\sp2){dollar}-centered bonding units. The model predictions are compared with the experimental results for typical amorphous a-C{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 FEM successfully predicts and explains some of the experimentally-observed properties of the above-mentioned alloys.
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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.
