Active oxygen sensors used a quartz crystal microbalance (QCM) with sputter-coated and spin-coated poly(tetrafluoroethylene) thin films

Organic thin films prepared by physical vapor deposition (PVD) have complex structures compared to the pristine materials. Therefore, these thin films have potentials to show different surface properties. Poly(tetrafluoroethylene) (PTFE) is one of the fluorocarbon polymers, and fluorocarbon thin films deposited by an r.f. sputtering with a PTFE target and spin coating with PTFE dispersion on a quartz crystal were investigated to determine their suitability for application in active oxygen sensors. Active oxygen generated under ultraviolet irradiation was successfully detected from frequency shifts using the QCM electrode coated with the fluorocarbon thin films. The sensitivity of the thin film prepared by the r.f. sputtering for active oxygen was higher than that of the thin film prepared by the spin coating. It is known that molecular structures of the fluorocarbon thin film prepared by the r.f. sputtering with a PTFE target were quite different from pristine PTFE. It is considered that this is one of the reasons why the sensitivity of the sputtered thin film for active oxygen was higher than that of the thin film prepared by the spin coating.