Nitrogen-incorporation induced changes in the microstructure of nanocrystalline WO3 thin films

Nitrogen incorporated tungsten oxide (WO3) films were grown by reactive magnetron sputter-deposition by varying the nitrogen content in the reactive gas mixture keeping the deposition temperature fixed at 400 °C. The crystal structure, surface morphology, chemical composition, and electrical resistivity of nitrogen doped WO3 films were evaluated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrical conductivity measurements. The results indicate that the nitrogen-incorporation induced changes in the microstructure and electrical properties of WO3 films are significant. XRD measurements coupled with SEM analysis indicate that the increasing nitrogen content decreases the grain size and crystal quality. The nitrogen concentration increases from 0 at.% to 1.35 at.% with increasing nitrogen flow rate from 0 to 20 sccm. The corresponding dc electrical conductivity of the films had shown a decreasing trend with increasing nitrogen content.