REGISTRATION OF SURFACE ACOUSTIC WAVES in Z-SECTIONS of PIEZOELECTRIC SINGLE CRYSTALS ZnO and CdS

Subject and Purpose. The subjects of this research are the internal electric field and the electric polarization vector, both existing in the volume of a deformed piezoelectric crystal. The work has been aimed at determining the dynamic electric polarization within the Z-section of a class 6 mm piezoelectric single crystal, deformed by surface acoustic waves (SAW), and estimating the sensitivity of the electrode pair of the inter-digit transducer in the mode of recording surface acoustic waves in Z-sections of the piezoelectric crystals. Methods and Methodology. The analysis proceeds from construction of a mathematical model for the SAW detector, through the use of an appropriate set of differential equations. It is taken into account that the electric charge on an electrode is determined by the vector of dynamic electric polarization and the the electric field distribution along the electrode. The effects of cross-sectional dimensions of the electrodes, the scattered electric field, and of the harmonic electrical polarization vector are taken into account. Results. Mathematical models have been constructed for a long electrode of finite cross-sectional dimensions, intended for surface acoustic wave (SAW) excitation in Z-sections of piezoelectric crystals of crystallographic class 6mm. The problem of calculating the electric charge distributions along the electrodes of the inter-digit transducer which operates in the SAW detector mode has been solved with account of the effects owing to the scattered electric field and harmonic wave motion of the electric polarization vector. Numerical values have been determined for the sensitivity of the inter-digit transducer operated in the receiving mode. In the case of ZnO and CdS single crystals the figures are 7.73·1010 and, 3.08·1010 V/m, respectively. Conclusions. A general solution to the boundary value problem of the internal electric field in the volume of a deformed piezoelectric has been obtained. The dynamic electric polarization has been determined within a Z-section plane of the single-crystal piezoelectric of class 6mm in the process of its interaction with a SAW. A mathematical model has been developed for a SAW detector, taking into account the effect of the electrodes’ cross-section size. The operating sensitivity of a pair of electrodes of the inter-digit transducer has been estimated for the SAW registration mode.