Piezopotential in a bended composite fiber made of a semiconductive core and of two piezoelectric layers with opposite polarities

We study the bending of a composite fiber of piezoelectric dielectrics and nonpiezoelectric semiconductors. The top and bottom piezoelectric layers are polarized in the opposite directions. A theoretical analysis is performed using a one-dimensional model. It is shown that mechanical loads trigger the redistribution of mobile charges in such a composite fiber. Thus the composite fiber exhibits piezotronic couplings like a homogeneous piezoelectric semiconducting fiber. The couplings are not a direct effect, but similar to a product property due to the particular design of the present composite. The electromechanical and semiconducting behaviors of the composite fiber and the effects of various parameters on piezotronic couplings are calculated and examined. It is observed that piezotronic couplings in these composite fibers are sensitive to material and geometric parameters and can be optimized through design. Different from the previous work on ZnO fiber where the mobile charges are driven to the top and bottom surfaces of the fiber, in the present composite fiber the mobile charges are driven to the two ends of the fiber. The present theoretical analysis of the composite fiber offers an important method for developing novel piezotronic devices.