Plasma-assisted deposition of chromium, fluorocarbon and chromium/carbon/fluorine films on glass, polymer and metal substrates
O'Keefe, Matthew J.
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https://hdl.handle.net/2142/19954
Description
Title
Plasma-assisted deposition of chromium, fluorocarbon and chromium/carbon/fluorine films on glass, polymer and metal substrates
Author(s)
O'Keefe, Matthew J.
Issue Date
1993
Doctoral Committee Chair(s)
Rigsbee, J. Michael
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Metallurgy
Engineering, Materials Science
Language
eng
Abstract
Sputter deposition of chromium (Cr), plasma polymerization of hexafluoroethane (C$\sb2$F$\sb6$), and plasma-assisted deposition of chromium/carbon/fluorine (Cr/C/F) thin films onto glass, polytetrafluoroethylene (PTFE), and low carbon, cold rolled steel substrates has been studied. Depositions were conducted in an internal electrode, radio frequency sputter deposition system at 100 W of power for one hour. Argon and C$\sb2$F$\sb6$ gases were used as the glow discharge media and characterization of the plasmas was done by optical emission spectroscopy. Fabrication of unique non-body centered cubic (non-BCC) Cr, plasma polymerized fluorocarbon, and optically transparent Cr/C/F thin films were done by non-equilibrium plasma processing.
The formation of a non-BCC, A-15 Cr crystal structure was found to be dependent on the concentration of oxygen in the chromium film. At oxygen atomic concentrations between 8-15% the Cr films were in a highly oriented (200) A-15 crystal structure while at O concentrations $>$15 at.% or $<$8 at.% the structure of the films was (110) oriented BCC Cr. Substrate material did not influence the crystal structure of the Cr films. Complete phase transformation of the A-15 Cr structure into BCC Cr occurred during vacuum annealing of the films at temperatures of T/T$\sb{\rm m}$ $\approx$ 0.3 and times on the order of one hour. Therefore, it was concluded that the A-15 Cr crystal structure is an impurity locked, metastable phase.
Optical emission characterization of C$\sb2$F$\sb6$ plasmas determined that the main species in the glow discharge was CF$\sb2$ and that an increase in the concentration of CF$\sb2$ species occurred if a graphite sputter target was used as the cathode material. The F/C ratio and distribution of CF$\sb3$, CF$\sb2$, CF, C-CF and C species in the deposited plasma polymerized films was dependent on the concentration of CF$\sb2$ species in the plasma and the substrate material. Differences in the chemical composition of the plasma polymerized films were attributed to an activated growth mechanism induced by ion bombardment.
Deposition of Cr/C/F films was done by reactive sputter deposition using a Cr target and an Ar/C$\sb2$F$\sb6$ plasma. The films were optically transparent up to 500 nm in thickness and crystalline. Determination of the exact crystal structure was not possible due to the complexity of the films. The chemical composition of the films was $\sim$35% Cr, $\sim$20% C and $\sim$45% F and could be controlled by varying the ratio of Ar to C$\sb2$F$\sb6$ in the gas feed.
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