Giant Flexoelectricity in Silicon via Light-Sensitive Schottky Junction

Silicon is the cornerstone material of modern electronics, and has industrialized techniques for achieving large-scale integration of functional devices. However, the lack of inversion symmetry breaking naturally determines its non-piezoelectricity, hindering the development of silicon-based electromechanics. Flexoelectricity induced by strain gradient is a promising way to endow silicon with electromechanical properties, but it is generally too weak to be functionalized in practical applications. Herein, a strategy is proposed to enhance the flexoelectricity of silicon by six orders of magnitude through the combination of a Schottky junction and light modulation. This flexoelectric-like effect arises from the bending-induced antisymmetric modulation on the Schottky barrier and the increase in carrier concentration generating by illumination. Under light illumination, the gold-coated n-type silicon yields a flexoelectric coefficient with six orders of magnitude larger than the intrinsic one, reaching a maximum of 1 mC m⁻¹. A mechanical energy harvester proto-device is further demonstrates the practicality of flexoelectrically modified silicon. The output normalized power density of the flexoelectric energy harvester is up to 2.5 µW cm³ g² Hz⁻¹, being comparable to the performance of lead-free piezoelectric ones. This work exploits the flexoelectricity in silicon, opening possibilities for high-performance electromechanical applications based on silicon.