Quantitative hydrocarbon sensor for ultra high vacuum applications

A promising new quantitative sensing device intended for hydrocarbon detection under stringent technological conditions is described. It exhibits good sensitivity and reproducibility, as well as a useful degree of selectivity. The sensor is based on a novel approach that exploits the well-known properties of the oxygen/yttria-stabilized zirconia/platinum solid-state electrochemical system. Correlated spectroscopic and electrochemical measurements provide fundamental insight into the mode of action under potentiostatic conditions:  the potential of the working electrode is set by the steady-state coverage of chemisorbed oxygen, which itself depends on the balance between rate of oxygen pumping to the Pt surface and the hydrocarbon impingement rate. Good quantitative agreement between theoretically predicted and measured hydrocarbon partial pressures is found. Nonlinearities that occur at sufficiently high hydrocarbon pressure are associated with the accumulation of small amounts of carbon at the surface of...