Phosphine Electrochemical Sensor Using Gold-Deposited Polytetrafluoroethylene Membrane

Phosphine gas is a toxic and flammable gas, which are useful dopant in the semiconducting industry. OSAH (Occupational Safety and Health Administration) regulates the threshold limit value as 0.3 ppm. To detect phosphine gas, an electrochemical sensor cell using gold as a working electrode is available. In this paper, we prepared Au thin film electrode on porous PTFE (polytetrafluoroethylene) membrane by using d.c. sputtering machine. Au thin film deposited on PTFE membrane for 300 s showed the thickness about 220 nm and electrical resistance between 5 and 10 ohm. We adopted this Au thin film as a working electrode and reference electrode. The sensitivity of the electrochemical cell is about 3000 nA/ppm for phosphine gas. Using Cottrell equation and COMSOL program, we simulated the diffusion coefficient of phosphine gas within the electrochemical cell, which showed the value of 1.21×10^-7 m²/s.