VUV Photodeposition of Thiol-Terminated Films: A Wavelength-Dependent Study
2018
Kasparek, Evelyne | Tavares, Jason R. | Wertheimer, Michael R. | Girard-Lauriault, Pierre-Luc
Photoinitiated chemical vapor deposition (PICVD) has become attractive for selective and specific surface functionalization, because it relies on a single energy source, the photons, to carry out (photo-) chemistry. In the present wavelength (λ)-dependent study, thiol (SH)-terminated thin film deposits have been prepared from gas mixtures of acetylene (C₂H₂) and hydrogen sulfide (H₂S) via PICVD using four different vacuum-ultraviolet (VUV) sources, namely, KrL (λₚₑₐₖ = 123.6 nm), XeL (λₚₑₐₖ = 147.0 nm), XeE (λₚₑₐₖ = 172.0 nm), and Hg (λ = 184.9 nm) lamps. Different λ influence the deposition kinetics and film composition, reflecting that photolytic reactions are governed by the gases’ absorption coefficients, k(λ). Thiol concentrations, [SH], up to ∼7.7%, were obtained with the XeL source, the highest reported in the literature so far. Furthermore, all films showed islandlike surface morphology, regardless of λ.
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