| Abstract
| - A potentiometric device based on interfacing a solid electrolyte oxygen ion conductor with a thin platinumfilm acts as a robust, reproducible sensor for the detection of hydrocarbons in high- or ultrahigh-vacuumenvironments. Sensitivities in the order of ∼5 × 10-10 mbar are achievable under open circuit conditions,with good selectivity for discrimination between n-butane on one hand and toluene, n-octane, n-hexane, and1-butene on the other hand. The sensor's sensitivity may be tuned by operating under constant current (closedcircuit) conditions; injection of anodic current is also a very effective means of restoring a clean sensingsurface at any desired point. XPS data and potentiometric measurements confirm the proposed mode of sensingaction: the steady-state coverage of Oa, which sets the potential of the Pt sensing electrode, is determined bythe partial pressure and dissociative sticking probability of the impinging hydrocarbon. The principlesestablished here provide the basis for a viable, inherently flexible, and promising means for the sensitive andselective detection of hydrocarbons under demanding conditions.
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