Nonlinear Mechanical And Electrical Properties Of Piezoelectric Semiconductors Rod Under Static And Dynamic Loads

Due to superior piezoelectric effect and semiconductor characteristics,piezoelectric semiconductors have been widely used in piezoelectric electronic devices and intelligent structures.A piezoelectric potential is generated when piezoelectric semiconductors are subjected to a mechanical load or deformation,and the piezoelectric potential drives the directional movement of electrons and regulates the transmission and transport of electrons.This self-powered performance of piezoelectric semiconductors greatly simplifies the structure of devices and facilitates the miniaturization of electron devices.For the development of new electro devices,it has important significant to study mechanical and electric properties in piezoelectric semiconductors based on the coupling relationships among deformation,electric field and electron.However,it is hard to find solutions of the mechanical problems due to the existence of the nonlinear coupling term between electric field and electron concentration in the constitutive relation.Therefore,the theoretical researches related mechanical and electrical performances in piezoelectric semiconductor are mostly based on the theory of small electron perturbation.The linearization of constitutive equation is only applicable when the small electron concentration perturbation is small thus it has certain limitations and is likely to bring errors in the results.Therefore,it is necessary to study the mechanical and electrical properties of piezoelectric semiconductors based on the true nonlinear constitutive relationship.In this dissertation,the following two aspects are studied for the typical nanowire structures of piezoelectric electronic devices under an axial mechanical load.1)Based on the nonlinear constitutive relation,a one-dimensional simplified rod model for piezoelectric semiconductor nanowire structures is established.Semi-analytical solutions of the electromechanical fields in the piezoelectric semiconductor rod under a static axial mechanical load are obtained with a homotopy analysis method and these solutions are compared with the analytical solutions based on linear constitutive relation.The influence of linearization of constitutive relation on displacement,electric potential and electron concentration and effects of applied electric field and initial electron concentration on the electric field distribution in the piezoelectric semiconductor rod are discussed.The nonlinear coupling relationship among deformation,electric field and electron and the regulation mechanism of mechanical load on the electric transmission characteristics in the piezoelectric semiconductors are revealed.2)Based on the one-dimensional simplified model proposed in 1),the vibration problem of piezoelectric semiconductor rod under sinusoidal excitation is studied with finite element method and an iterative process in combination,and the numerical solutions of electromechanical field responses of piezoelectric semiconductor rod are obtained.The differences of the elastic displacement,electric potential and electron concentration perturbation obtained based on the linear constitutive and nonlinear constitutive relationship are compared.The necessity of studying the piezoelectric semiconductor mechanical and electrical properties based on the nonlinear constitutive relationship is revealed.The effects of initial electron concentration and sinusoidal excitation amplitude on elastic displacement,electric potential and carrier concentration vibration are numerically discussed.The interaction between elastic wave and electro under dynamic load is shown.It is found that a higher initial electron concentration can amplify the elastic wave due to the electron shielding effect,and the electron concentration gradually presents fluctuate with the increase of the amplitude of sinusoidal excitation.