Abstract
The gas barrier property of a silicon oxide (SiOx) film synthesized from plasma-enhanced chemical vapor deposition using the tetramethysilane (TMS)-oxygen gas mixture was modified by introducing ammonia gas in the glow discharge. The change in the glow discharge with the ammonia gas incorporation was monitored by an optical emission spectrometer (OES). Structures, chemical bond configurations, and material properties of the resulting films were investigated. The introduced ammonia gas in the TMS-oxygen plasma resulted in emission lines dominated by the N2 and CN species with the suppression of the OH and oxygen-related radicals, thereby introducing nitrogen and carbon atoms in the deposited film. A silicon oxynitride (SiOxNy) film had the best surface morphology and the lowest residual internal stress was achievable by controlling the reactant gas flow ratio of the ammonia and oxygen. The barrier property to the water vapor permeation of the silicon oxide film (~1.65 g/m2/day) deposited onto the polyethylene terephthalate (PET) substrate was thus greatly improved to 0.06 g/m2/day for the film synthesized from an adequate TMS-oxygen-ammonia gas mixture.
Highlights
Silicon oxide (SiOx ) film is comprehensively deposited for passivation, insulation, waveguide, detector and sensor, and anti-reflection applications, as it has many advantages over other materials such as optical transparency with a low refractive index, impact resistance, and environmental and chemical stability [1,2,3,4]
The optical emission spectra recorded from the glow discharge of the TMS-O2 -NH3 gas mixture at an ammonia gas flow ratio of 0 (i.e., TMS-O2 gas mixture) and 0.5 are shown in Figure 1a,b, respectively
The hydrogen- and nitrogen-related emission lines that came from the dissociation of ammonia became the fingerprint of the optical emission spectrometer (OES) spectrum observed from the glow discharge of the TMS-O2 -NH3 gas mixture
Summary
Silicon oxide (SiOx ) film is comprehensively deposited for passivation, insulation, waveguide, detector and sensor, and anti-reflection applications, as it has many advantages over other materials such as optical transparency with a low refractive index, impact resistance, and environmental and chemical stability [1,2,3,4] This glassy coating which offers the conditions for a barrier layer against moisture, gas, and aromas has been employed for deposition onto plastic substrates for packaging applications [5,6]. Lau et al investigated the optical and material properties of the sputtered -SiO2 , -SiOx Ny , and -Si3 N4 films They found that the barrier property of the SiO2 film to water vapor permeation was quantitatively improved with low nitrogen contents in the reactive gas mixture due to the optimization of the mechanical stress and the enhancement of the coating density [11]. The impact on the surface roughness, particle morphology and residual internal stress of the deposited films synthesized from the ammonia gas introduced into the TMS-O2 gas mixture were elucidated
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