Atomic layer deposition of environmentally benign SnTiOx as a potential ferroelectric material.

Inspired by the need to discover environmentally friendly, lead-free ferroelectric materials, here the authors report the atomic layer deposition of tin titanate (SnTiOx) aiming to obtain the theoretically predicted perovskite structure that possesses ferroelectricity. In order to establish the growth conditions and probe the film structure and ferroelectric behavior, the authors grew SnTiOxfilms on the commonly used Si(100) substrate. Thin films of SnTiOx have been successfully grown at a deposition temperature of 200 °C, with a Sn/Ti atomic layer deposition(ALD) cycle ratio of 2:3 and postdeposition heat treatments under different conditions. X-ray photoelectron spectroscopy revealed excellent composition tunability of ALD.X-ray diffraction spectra suggested anatase phase for all films annealed at 650 and 350 °C, with peak positions shifted toward lower 2-theta angles indicating enlarged unit cell volume. The film annealed in O2 at 350 °C exhibited piezoresponse amplitude and phase hysteresis loops, indicative of the existence of switchable polarization.