Theoretical Analysis Of Flexoelectric And Strain Gradient Effects In One-Dimensional Piezoelectric Semiconductors

Because of the dual physical properties of both piezoelectric materials and semiconductor materials,piezoelectric semiconductors have attracted more and more attentions in recent years and have become one of the most cutting-edge materials in the field of smart devices.Among many piezoelectric semiconductor structures,onedimensional piezoelectric semiconductors composed of nanofibers are one of the important structural forms of electronic components.However,in recent years,some experiments have shown that materials in micro-and nano-scale also show a series of different properties from those in macro-scale,that is,they have scale effect.Therefore,the theoretical study of the scale effect of one-dimensional piezoelectric semiconductors,including strain gradient and flexoelectric,has important guiding value for the design of smart structural elements in micro-and nano-scale.Considering the flexoelectric effect and strain gradient effect,the following work is carried out in this thesis:(1)Considering flexoelectric effect and strain gradient effect,the tension of onedimensional piezoelectric semiconductors is analyzed,and the analytical expressions of related physical quantities are obtained.After that the electric potential,carrier concentration,electric displacement and electric field distribution are calculated,and the effects of flexoelectric effect and strain gradient effect on the physical fields are analyzed.The results show that the both two effects have influence on the distribution of the physical field,and the magnitude of the influence depends on the flexoelectric coefficient and the inner scale coefficient.(2)The bending of one-dimensional piezoelectric semiconductor cantilever beam considering flexoelectric effect and stress gradient effect is analyzed by using firstorder beam theory,and the analytical expressions of deflection,rotation angle,electric potential and carrier concentration are obtained.The effects of flexoelectric effect and strain gradient effect on the distribution of physical field are analyzed.The results show that both effects have influence on the distribution of physical fields and the magnitude of the influence depends on the flexoelectric coefficient and the inner scale coefficient.This work lays a foundation for the further study on the size effect of piezoelectric semiconductors,provides theoretical support for the design and development of microand nano-scale piezoelectric semiconductor devices,and is of great value for guiding practical engineering application.