Chemical characterization of plasma-polymerized films from acetylene and nitrogen-containing mixtures and their ethanol vapor sensitivity

In this study, plasma-polymerized thin films were prepared from plasma enhanced chemical vapor deposition (PECVD) of acetylene (C2H2), acetylene/nitrogen (C2H2/N2), or acetylene/ammonia (C2H2/NH3). When N2 or NH3 was mixed with C2H2 in the feed, the films were identified to contain all elements of the mixture and the properties of the films were implied by the C-H bonds and nitrogen functionalities. As shown by X-ray photoelectron spectroscopy (XPS) the [N]/[C] atomic ratio varies by changing the mixture composition and reaches a maximum of 0.12 for mixing C2H2 with NH3. It is found that the resistance of the thin film sensors prepared from C2H2, C2H2/N2, and C2H2/NH3 is distinctly decreased by over 2 orders of magnitude by the adsorption of ethanol vapor.