Nanogenerator with direction sensitive piezoelectric response based on InGaN nanowires over ridge textured Si (1 1 0) substrate with inter-facet topography modulation

Highlights: • InGaN NWs with inter-facet tuned inclination orientation were grown by PA-MBE. • The asymmetric piezoelectric output is investigated by AFM in contact scan mode. • The fabricated PNG device shows force direction sensitive piezoelectric response. Direction sensitive piezoelectric response is demonstrated from a nanogenerator based on an InGaN nanowires array on a ridge textured Si (1 1 0) substrate with inter-facet topography modulation. Under stationary molecular beam epitaxy, distinct variations of the inclination orientation of the InGaN nanowires are created due to the different beam flux incidence angle between the facets, which act as the primary factor for the asymmetric piezoelectric output. The piezoelectric properties were first studied using an electrical atomic force microscope (AFM) in contact scan mode at zero bias. The InGaN NWs on opposite ridge facets show different piezoelectric output distribution under the same scanning geometry. The difference of the tangential force component due to the varied NWs tilting angle, applied on the NWs by the AFM probe tip, explains the non-uniform piezoelectric signal distribution. A capacitor type piezoelectric nanogenerator (PNG) device was fabricated, which exhibits pronounced direction sensitive piezoelectric response under rotated external pressure. This work gives a universal strategy on synthesis of composite semiconductor materials with anisotropic piezoelectric response in terms of a self-powered force direction sensitive angle sensor piezoelectric nanogenerator device.