RFBR project No. 20-07-00139 (2020-2022) “Backward acoustic waves in highly anisotropic materials and structures based on them”
Head: Ph.D. Kuznetsova A.S.
One of the types of acoustic waves propagating in the plates are backward acoustic waves with different polarizations. The phase and group velocities of these waves are directed in different directions.
The aim of this project is a theoretical and experimental study of the features of excitation and propagation of backward acoustic waves in highly anisotropic materials and structures based on them and containing, among other things, piezoelectric and piezosemiconductor layers under various boundary conditions. As a result of the project, the following major results were obtained:
- Crystallographic orientations of TeO2 were discovered for the first time, at which the existence of backward acoustic Lamb waves of various types is possible. The backward acoustic antisymmetric wave of the first order (A1), which exists in TeO2 at Euler angles φ=θ= ψ =0, has been studied in detail. The effect of a strong piezoelectric layer (lithium niobate) on the characteristics of this wave was investigated. It has been found that with an increase in the thickness of the lithium niobate layer, the backward wave velocity increases, and the point with zero group velocity shifts to lower frequencies. In this case, the wave type did not change.
- The effect of an infinitely thin layer with arbitrary conductivity on the characteristics of the A1 backward wave in the structure “TeO2 plate – LiNbO3 plate” is studied. It is shown that as the layer conductivity increases, the velocity of backward acoustic waves in such structures increases.
- The effect of a layer of a piezo-semiconductor material (gallium arsenide) on the characteristics of the detected backward A1 wave has been studied. It is shown that, as in the case of a layer with a strong piezoelectric material, with an increase in the thickness of the piezoelectric semiconductor layer, the backward wave velocity increases, and the point with zero group velocity shifts to lower frequencies. It should be noted that in the case of a piezoelectric semiconductor, this displacement is larger than in the case of a strong piezoelectric material, despite the weak piezoelectric effect. This is due to the allowance for the conductivity of the layer material. In this case, the wave type did not change.
- The effect of an infinitely thin layer with arbitrary conductivity on the characteristics of the A1 backward wave in the structure “TeO2 plate – GaAs plate” is studied. It has been found that the bulk conductivity of the GaAs wafer almost completely screens the piezoelectric effect of TeO2, which leads to the almost complete absence of the influence of the layer with arbitrary conductivity, which contacts the piezoplate from the reverse side, on the velocity of backward acoustic waves.
- A technology has been developed for manufacturing structures “TeO2 plate – metal-ZnO film” Interdigital transducers were placed on the surface of the ZnO film. The possibility of excitation of acoustic waves in such structures is shown. At the same time, the registration of backward waves in such a structure requires additional efforts.
In general, it should be noted the need for additional research in terms of creating and using structures containing strong piezoelectrics on one side of paratellurite and piezoelectric semiconductors on the other side of paratellurite. This task will be considered further.
During the project, 4 articles were published:
- Zhao Z., Wang B., Qian Z., Kuznetsova I., Ma T., Yong Y.K. Design considerations for frequency shifts in a laterally finite FBAR sensor in contact with the Newtonian liquid// IEEE Trans. on Ultrasonics, Ferroelectrics, and Frequency Control, 2020, v.67, #11, pp.2402-2412, DOI: 10.1109/TUFFC.2020.3006186, Q1.
- Fang K., Li N., Li P., Qian Z., Kolesov V., Kuznetsova I. A convenient approach to tuning the local piezopotential of an extensional piezoelectric semiconductor fiber via composite structure design // Nano Energy, 2021, v.90, p.106626, DOI: 10.1016/j.nanoen.2021.106626, Q1.
- Fang K., Li P., Li N., Liu D., Qian Z., Kolesov V., Kuznetsova I. Model and performance analysis of non-uniform piezoelectric semiconductor nanofiber// Applied Mathematical Modelling, 2022, v.104, 628-643, 10.1016/j.apm.2021.12.009, Q1
- Qian Z., Li P., Lu M., Kuznetsova I., Kolesov V., Ma T. Flexural wave control via the profile modulation of non-uniform Timoshenko beams// Mechanics of Materials, 2022, v.165, p.104162, 10.1016/j.mechmat.2021.104162