Several Typical Guided Waves Propagating In Different Structures Of The Piezoelectric Semiconductor

With the development of micro-electromechanical technology, piezoelectric semiconductor materials with properties of mechanic-electric coupling and semiconductor have attracted much attention. Piezoelectric materials with semiconducting properties represented by ZnO can be used in new type micro-electro-mechanical acoustic wave devices. In this thesis, based on the basic theories of elastic dynamics, we make modeling analysis, theoretical calculation and data analysis about several typical guided waves propagating in different structures of piezoelectric semiconductor under the coupling influence of piezoelectric effect,semiconductor characteristics and bias fields. The main consists as follow.(1) The propagation characteristics of several typical guided waves in transversely isotropic piezoelectric semiconductor structures are analyzed and discussed. Based on the constitutive equation, the relation between displacement and strain, the governing equation, a set of partial differential equations of the governing equation expressed by displacement function, electric potential and function of carrier concentration is established. The analytical equations of wave velocity and wave number are obtained by considering the boundary conditions of stress free and electrical continuity.(2) Based on the above analytical model, the propagation characteristics of the generalized Rayleigh wave in the half-space piezoelectric semiconductor, and SH wave and Lamb wave in the piezoelectric semiconductor film are analyzed. It is found that the generalized Rayleigh wave can be propagated in the half-space piezoelectric semiconductor and the properties of semiconductor led to dispersion of wave. The SH wave and the Lamb wave can also be spread in piezoelectric semiconductor film, and multiple dispersion modes exist in the film of piezoelectric semiconductor; The phase velocity of guided waves propagating in the piezoelectric semiconductor are influenced and attenuated by the properties of semiconductor. When a large enough bias electric field is exerted along with the direction of guided wave we can get gain waves.After this research we found that the characteristics of wave attenuation or gain can be affect by the semiconductor effect and the bias electric field effect. The conclusion we drew can guide the design of acoustic devices that represented by ZnO and other piezoelectric semiconductor materials. It is expected to provide the theoretical basis and support for the non-destructive testing of ultrasonic materials in new intelligent materials and structures.