Effects of sputtering pressure on compositions and structures of fresnoite thin films

Fresnoite is a new ferroelectric mineral which has potential applications in acoustic wave devices and non-linear optical devices. In this paper, fresnoite thin films were fabricated by r.f. sputtering. The experiments indicated that the working pressure influences significantly on the composition and structure of the thin films. As the pressure decreases, the deficiency of Ba and the excess of Si in the thin films were controlled. A thin film with chemical stoichiometry was obtained at the pressure of 0.3 Pa. Besides, the decrease of the pressure improved the crystallinity and orientation of the thin films. These improvements on the stoichiometry and microstructure of the fresnoite thin films are attributed to the increase of the mean free path and the impacting energy of ions at low working pressure.