Correlation between ferroelectric polarization and conductive nanobits in epitaxial SrTiO₃ thin films with controlled deposition rates

Although SrTiO₃ (STO) thin films are paraelectric at room temperature, ferroelectricity can be induced either by epitaxial strain or by the generation of oxygen vacancies. Furthermore, the application of an external voltage enables the modulation of oxygen vacancies, which in turn facilitates the formation of conducting filaments and resistive switching characteristics. In this study, we investigated ferroelectric polarization nanobits and conductive filament nanobits within epitaxial STO thin films using scanning probe microscopy. The STO thin films with tetragonal strain on single-crystal Au substrates exhibited room-temperature ferroelectricity. The possibility of oxygen vacancies occurring within these conductive filament nanobits was confirmed during the formation process of conductive filament nanobits in a local area by conducting atomic force microscopy. In the observation of ferroelectric polarized nanobits by piezoresponse force microscopy, an increase in the polarization size of ferroelectric polarized nanobits was observed due to an increase in the oxygen vacancy concentration. The results provide opportunities for nonvolatile memory applications utilizing the formation of conductive filamentary nanobits by controlling the oxygen vacancy concentration generated within the STO thin film and the enhanced polarization of ferroelectric polarized nanobits by controlling the oxygen vacancy concentration.