Ultrasonic Microspectroscopy Characterization of AlN Single Crystals

Abstract

Basic acoustic properties of AlN single crystal Y -cut and Z -cut plates, grown by the physical vapor transport method, were evaluated using ultrasonic microspectroscopy (UMS) technology. A method of determining the acoustical physical constants with two specimens was developed by measuring the velocities of longitudinal and shear waves and leaky surface acoustic waves (LSAWs). We obtained accurate bulk-wave velocities, LSAW velocities and their distributions in the specimen surfaces, and the density with great differences compared with the calculated ones using the reported constants. We also determined the corresponding constants. This UMS technology will contribute to the further development of AlN crystals. #

Effect of Sc concentration on shear wave velocities in ScAlN films measured by micro-Brillouin scattering technique

“…These elastic constants c 66 , c 11 and c 33 D were determined by the ultrasonic microscopy and Lamb wave devices. Here, we calculated the velocity values from the elastic constant reported by Tanaka's group by assuming that the mass density ρ is 3260 kg/m 3 [6]. As shown in Fig.…”

“…Our group first reported the softening of longitudinal wave velocities (c 33 D /ρ) 1/2 . A 30-40% decrease of the velocity compared the single crystalline AlN was observed in the ScAlN films [5,6]. Moreira et al also reported the decreasing of elastic constants c 33 E in ScAlN film bulk acoustic resonators (FBARs) with Sc concentrations of 0-15% [7].…”

“…Moreira et al also reported the decreasing of elastic constants c 33 E in ScAlN film bulk acoustic resonators (FBARs) with Sc concentrations of 0-15% [7]. Matloub et al investigated the longitudinal wave velocity (c 33 D /ρ) 1/2 in a ScAlN FBAR with Sc concentration of 12 %, and showed that the velocity (10300 m/s) was lower than that of a single crystalline AlN (11132 m/s) [6,8]. Our group previously investigated the longitudinal wave velocities v = (c 33 D /ρ) 1/2 in ScAlN films with high Sc concentrations of 0-63% [9].…”

Polarity-inverted ScAlN film growth by ion beam irradiation and application to overtone acoustic wave (000-1)/(0001) film resonators

“…Theoretical conversion efficiency curves were simulated using Mason's equivalent circuit model. 20 The density q and the dielectric constant e 33 reported for an AlN single crystal 24 were used in this model, and the longitudinal wave velocity in this model was set to 75% of that of an AlN single crystal. 24 The fundamental mode acoustic resonance was excited around 2 GHz, and the excitation of a second-overtone mode acoustic resonance was not observed in both resonators.…”

Electromechanical coupling and gigahertz elastic properties of ScAlN films near phase boundary

“…The velocity of the Sc 0.41 Al 0.59 N film near the phase boundary was 8020 m/s, which is 72% of 11132 m/s, the value for an AlN single crystal. 17 Figure 1(d) shows k t 2 as function of the Sc concentration. The solid circles show k t 2 extracted from the HBARs (including a substrate).…”