Using a high-resolution X-Ray diffraction measurement method, the surface acoustic wave (SAW) propagation in a graphene film on the surface of a Ca₃TaGa₃Si₂O₁₄ (CTGS) piezoelectric crystal was investigated, where an external current was driven across the graphene film. Here, we show that the application of the DC field leads to a significant enhancement of the SAW magnitude and, as a result, to amplification of the diffraction satellites. Amplification of 33.2 dB/cm for the satellite +1, and of 13.8 dB/cm for the satellite +2, at 471 MHz has been observed where the external DC voltage of +10 V was applied. Amplification of SAW occurs above a DC field much smaller than that of a system using bulk semiconductor. Theoretical estimates are in reasonable agreement with our measurements and analysis of experimental data for other materials.

X-ray diffraction on the $X$ cut of a langasite crystal $({\mathrm{La}}_3{\mathrm{Ga}}_5{\mathrm{SiO}}_{14})$ modulated by a $\text{Λ=12\hspace{0.17em}μ}\mathrm{m}$ Rayleigh surface acoustic wave (SAW) has been studied at the ESRF synchrotron radiation source. Due to the sinusoidal modulation of the crystal lattice involved by the SAW diffraction satellites appear on the rocking curve, with their number, angular positions, and intensities depending on the amplitude and wavelength of the ultrasonic superlattice. Full extinction of a specific satellite could be performed by adjusting the acoustic amplitude. It is shown that x-ray diffraction can be used to study surface acoustic wave field distributions in crystals.

This paper reports a scanning electron microscopy investigation of surface acoustic wave propagation in the LiNbO/sub 3/ crystals with regular domain structures. The regular domain structures in the LiNbO/sub 3/ crystals were formed by the method of the thermo-electric treatment after growth. We investigated two modes of the interaction between the surface acoustic waves and regular domain structures in the LiNbO/sub 3/ crystals: excitation of the surface acoustic waves by the curved regular domain structure, and propagation of the surface acoustic waves along and across the regular domain structures. It is shown that the regular domain structure in the first case can be used as an interdigital transducer for excitation of the surface acoustic waves through the longitudinal piezoelectric effect. In the second mode of the interaction we observed that the regular domain structure can be used as an acoustic wave-guide in the process of the propagation of the traveling surface acoustic waves along the regular domain structure. Also, we demonstrate the reflection of the surface acoustic waves from the domain walls in the process of surface acoustic wave propagation across the regular domain structure.<>

Electrical conductivity and acoustic loss Q⁻¹ of single crystalline Li(Nb,Ta)O₃ solid solutions (LNT) are studied as a function of temperature by means of impedance spectroscopy and resonant piezoelectric spectroscopy, respectively. For this purpose, bulk acoustic wave resonators with two different Nb/Ta ratios are investigated. The obtained results are compared to those previously reported for congruent LiNbO₃. The temperature dependent electrical conductivity of LNT and LiNbO₃ show similar behavior in air at high temperatures from 400 to 700 °C. Therefore, it is concluded that the dominant transport mechanism in LNT is the same as in LN, which is the Li transport via Li vacancies. Further, it is shown that losses in LNT strongly increase above about 500 °C, which is interpreted to originate from conductivity-related relaxation mechanism. Finally, it is shown that LNT bulk acoustic resonators exhibit significantly lower loss, comparing to that of LiNbO₃.