Asymmetric behavior in flexible piezoelectric strain sensors made of single ZnO nanowires.

Abstract

Piezoelectric strain sensors were fabricated using single ZnO nanowires on flexible polystyrene substrates and the asymmetric behavior in this kind of piezoelectric strain sensor made of single nanowire was firstly introduced. The I~V curves of the sensors under a serious of tensile and compressive strains were measured and agreed with the thermionic emission-diffusion theory. The Schottky barrier heights were obtained. The change in Schottky barrier heights of the sensors under compressive strain is much slower than that under tensile strain and the asymmetric elastic response of the sensors is caused by the bending of the ZnO nanowires under compressive strains when the applied strain is larger than a critical strain εcr. And the conclusion that the critical strain εcr only relates to the geometry parameters of the nanowire is drawn. The reduction of the axial compressive strain in compression was calculated. This asymmetric behavior in strain sensors is firstly introduced and is important for the design and fabrication of this type of strain sensors.