Sensing Properties of E-Beam Evaporated Nanostructured Pure and Iron-Doped Tungsten Oxide Thin Films

Gas sensing properties of nanostructured pure and iron-doped WO(3) thin films are discussed. Electron beam evaporation technique has been used to obtain nanostructured thin films of WO(3) and WO(3):Fe with small grain size and porosity. Atomic force microscopy has been employed to study the microstructure. High sensitivity of both films towards NO(2) is observed. Doping of the tungsten oxide film with Fe decreased the material resistance by a factor of about 30 when exposed to 5 ppm NO(2). The high sensitivity is attributed to an improved microstructure of the films obtained through e-beam evaporation technique, and subsequent annealing at 300 degrees C for 1 hour.