Hyper-efficient mechanical switching of ferroelectric polarization on metastable perovskite ferroelectric thin films

Feasibility of domain switching through mechanical force (i.e. in the absence of electric field) by scanning-probe-induced strain gradient suggests an alternative way to switching the ferroelectric polarization, attracting much interest in the application for ferreoelectric-based devices. Therefore, ultra-low mechanical switching load can lead to a new strategy for realizing of low energy electronics because it could reduce the energy costs for information storage in nanoscale mechanoelectric devices.

Recently, the successful growth and characterization of perovskite (111)-oriented CaTiO₃ (CTO) thin films in which the room temperature ferroelectricity is induced by stabilizing oxygen octahedral rotation (OOR) pattern in our group. Therefore, this system is suitable for the investigation of efficient mechanical switching of ferroelectric polarization due to the existence of multiple coupled atomic distortions. Thus, in this study, we focus on energy-efficient enhanced mechanical switching of ferroelectric polarization on CTO films via multiple coupled atomic distortions. Ferroelectric and mechanical properties of epitaxially (111)-oriented perovskite ferroelectric CTO thin films on (111) LaNiO₃ (LAO) /LaAlO₃ (LAO) substrate grown by pulsed laser deposition is explored. In this CTO films, low mechanical switching force (F_L) down to ~100 nN is obtained. This value is considerably lower than the reported one (> 300 nN). Remarkably, reduced mechanically written domain line width to ~10 nm by this low switching force is found in CTO films, suggesting the high recording density of up to 1 Tbit/cm². Our results would give new opportunities to achieve low energy nanoelectronics using ferro- and flexoelectric domain switching on oxide thin films.