Epitaxial growth of WO3 films on SrTiO3 and sapphire

Tungsten trioxide films were deposited on (100) SrTiO3 and R-plane (10 (1) over bar 2) cut sapphire substrates by de magnetron sputtering, using a tun gsten target in an Ar/O-2 sputtering gas mixture at substrate temperatures ranging from 500 to 850 degrees C. Deposited films were characterized by x- ray diffraction using theta-2 theta scans and pole figure analysis. X-ray r esults showed that films deposited on both types of substrate were epitaxia l. The equilibrium phase was monoclinic gamma-WO3, confirmed by Raman spect roscopy. Films on both substrates were (001) oriented. This preferred orien tation improved as the deposition temperature was reduced. The in-plane ori entation relationship of the films with the substrate was obtained from the pole figures.