Effect of Si addition on epitaxial growth and gas sensing properties of tungsten oxide films

WO3 epitaxial films with the same thickness and in-plane crystal grain size were prepared using pulsed laser deposition with various Si contents in the target to clarify the effect of Si addition to WO3 on the gas sensing properties. X-ray diffraction measurements indicated that the films grown on the (1 (1) over bar 02) face of sapphire had a (001) orientation with in-plane epitaxial relationships of [110]WO3//[01 (1) over bar1] or [110]WO3//[2 (1) over bar 10]Al2O3, regardless of the Si content. Scanning probe microscopy observations revealed that particles with a diameter of several tens of nanometers grow on the surface of the Si-doped WO3 film. Measurements of the gas response to ethanol and acetone showed superior gas selectivity towards acetone gas at low temperatures, which is due to the catalytic effect of SiOx particles on the film surface.