IMF2017

We studied ferroelectricity and photovoltaic effects in 40-nm-thick SnTiO_x films grown directly onto a p-type (001) Si substrate by atomic layer deposition (ALD). These films showed well-saturated, square, repeatable hysteresis loops with 1.5 mC/cm² remnant polarization at room temperature, as detected by out-of-plane polarization versus electric field (P-E) and field-cycling measurements. A photo-induced enhancement in ferroelectricity was also observed as the spontaneous polarization increased under white light. The SnTiO_x films exhibited relaxor characteristics with the dielectric constant peak shifting from ca. T = 600 K at f = 1 MHz to ca. 500 K at 100 Hz. Moreover, our films showed ferroelectric photovoltaic behaviour under the illumination of a wide spectrum of light, from visible to ultraviolet regions. A combination of experimental and theoretical calculations determined the optical band gap of the SnTiO_x films, which was found to lie in the visible range of the white light spectrum. Our study paves the way for the development of green ferroelectric SnTiO_x thin films that are compatible with semiconducting processes and can be used for various ferroelectric and dielectric applications.