Investigation of External Charges Effects on Piezoelectric ZnO Nanogenerator

Abstract

Piezopotential generation in semiconductive ZnO nanowire (NW), oriented along the c-axis [0001], is significantly affected by free charge carriers within the ZnO NW. In this paper, the effect of free carriers’ distribution in semiconductive ZnO nanowire is investigated, using a Finite Element Method (FEM). The mentioned effect leads to modification of the conduction band variation, carrier concentration profiles, and eventually, the magnitude and distribution of the piezoelectric potential. The impact of free charge carriers shows that the negative potential distributed at the tip of ZnO NW is decreased from V = – 270 mv for the donor concentration ND = 1 × 1015 C/m3 to the V = – 25 mV, in presence of the donor concentration of ND = 1 × 1018 C/m3. With selecting the appropriate electrical boundary conditions and applying the surface charges density at the top of the nanowire, the potential reduction is compensated. The electrostatic effect leads to a significant enhancement of the piezoelectric potential. The results are well shown the interplay of volume and surface charges and their influence on performance of nanogenerator, and so are crucial for designing of nanogenerators with high piezoelectric potential and good efficiency.