Non-volatile Tuning of Mechanical Resonance in Ultra-thin Single-Crystalline BaTiO3 Microbridges on Si(100) through Transient Applied Stress.

Ferroelectric materials exhibit complex and dynamic free energy landscapes that enable non-volatile functionality in electronic devices. While ferroelectrics have primarily been exploited to realize non-volatile electrical behavior, here we explore non-volatile mechanical behavior. We present the structural and resonant mechanical behavior of ultra-thin microbridges fabricated from single-crystalline BaTiO3 that has been epitaxially grown on Si(100). The microbridges exhibit both in-plane and out-of-plane domain variants. The mismatch in thermal expansion between the Si and the epitaxial BaTiO3 gives rise to residual tensile strain that enhances the resonance frequencies of the microbridges. We find that transient applied mechanical stress leads to non-volatile enhancements in the mechanical resonance frequencies of the microbridges, indicating a stiffening of BaTiO3. Phase-field modeling reveals that applied mechanical stress re-orients out-of-plane domain variants to in-plane variants, thereby enhancing the Young's modulus of BaTiO3. The ability to induce non-volatile changes in mechanical resonance through applied stress enables device functionalities in nanoelectromechanical systems.