Highly sensitive hydrogen sensors based on co-sputtered platinum-activated tungsten oxide films

Platinum-activated tungsten oxide (Pt–WO3) films for highly sensitive hydrogen (H2) sensors were co-deposited using radio frequency (r.f.) sputtering with subsequent two-step heat treatments. The Pt–WOx films were annealed at 700 °C for 1 h and then thermally treated at 450 °C for 24 h or 48 h. The microstructure, crystalline phase and composition of the as-sputtered, annealed and thermally treated films were characterized with scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The sensors were tested for 30–200 ppm H2 in air at different temperatures from 95 to 220 °C and with a relative humidity from 0 to 75%. The influences of Pt concentration and thermal treatment on the microstructure and the sensing performances of the Pt–WO3 films are presented in this work.