Typical transient effects in a piezoelectric semiconductor nanofiber under a suddenly applied axial time-dependent force

Based on the mechanical motion equation,Gauss’s law,and the current continuity condition,we study a few typical transient effects in a piezoelectric semiconductor(PS)fiber to realize the startup and turning-off functions of common piezotronic devices.In this study,the transient extensional vibration induced by a suddenly applied axial time-dependent force is examined in a cantilevered n-type ZnO nanofiber.Neither the magnitude of the loadings nor the doping concentration significantly affects the propagation caused by disturbance of the axial displacement.However,both of the factors play an important role in the propagation caused by disturbance of the electron concentrations.This indicates that the electromechanical coupling effect can be expected to directly determine the electronic performance of the devices.In addition,the assumption of previous simplified models which neglect the charge carriers in Gauss’s law is discussed,showing that this assumption has a little influence on the startup state when the doping concentration is smaller than 1021 m-3.This suggests that the screening effect of the carriers on the polarized electric field is much reduced in this situation,and that the state is gradually transforming into a pure piezoelectric state.Nevertheless,the carriers can provide a damping effect,which means that the previous simplified models do not sufficiently describe the turning-off state.The numerical results show that the present study has referential value with respect to the design of newly multifunctional PS devices.

Transient Bending Vibration of a Piezoelec trie Semiconductor Nanofiber Under a Suddenly Applied Shear Force

We study transient bending vibration of a ZnO piezoelec trie semiconduc tor nanofiber fixed at one end with a suddenly applied shear force at the other end.A one-dimensional model based on the phenomenological t heory of piezoelec trie semiconductors consisting of the equations of piezoelectricity coupled to the continuity equation of electrons is used.An approximate theoretical analysis is performed,accompanied by a finite element analysis using COMSOL.The evolutions of deflection,elec trie pot ential and elec tron dist ribution are calculated and examined.It is found that when the fiber reaches its largest deflection,the distributions of the electromechanical fields are qualitatively similar to those in the case of static loading under the same shear force,but the amplitudes of the fields are about twice as large roughly.