Microwave acoustic studies of materials in diamond anvil cell under high pressure

This paper presents an integrated measuring system combining a diamond anvil cell (DAC) and a high overtone bulk acoustic resonator (HBAR) operating at the microwave frequency band as 2.8–8.8 GHz. We have studied several metallic (W, Zr) and semiconductor (Si) samples under pressure up to ∼16 GPa. As an HBAR, we have used the “Al/Al0.72Sc0.28N/Mo/(100) diamond” structure utilizing a piezoelectric aluminum–scandium nitride film. We have observed that under pressure, the Q-factor of the HBAR decreases but remains at the value of 2500–3000, which is suitable for our experiments. It is demonstrated that the above system can be used for studying the behavior of various solids under high pressure, the pressure-induced phase transition in Zr, the registration of plastic deformations, and their relaxation in metals. Here, we discussed the phenomenon of an acoustic wave passing through a tungsten layer under a pressure of ∼5.5 GPa. The integrated DAC&HBAR measuring system has demonstrated some practical advantages over known ultrasonic systems combined with the DAC as the possibility of applying a microwave operational frequency, the measurement of a Q-factor change under pressure, and the miniature size of a sensitive HBAR element. The application of the built-in DAC&HBAR system will hopefully allow more accurate studies on materials in the GPa pressure range of a DAC.