Ag induced modifications on WO3 films studied by AFM, Raman and x-ray photoelectron spectroscopy

In this paper, the morphology, vibrational spectra and electronic properties of WO3 films loaded with different levels of Ag, prepared by screen printing onto Si substrates and annealed in air at 600degreesC were investigated. AFM micrography showed that the films are grain-like, and the grain size increases with an increase in the Ag loading level. Raman spectroscopy results showed the formation of a AgWO3 bronze structure that results in a more stable film. X-ray photoelectron spectroscopy results showed that the Ag concentration is 1.8 times higher than the nominal concentration indicating that Ag diffuses to the WO3 grain surface. No strong electronic interaction between the Ag clusters and the WO3 grains was found. Sensors fabricated with the WO3 : Ag films exhibited a significant increase in their sensitivity and selectivity towards NO2 detection.