Fig 3 - uploaded by Takahiko Yanagitani
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The changes of the lattice strains of the ScAlN (Sc:31.2%) resonator without removing a substrate (HBAR).
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... í µí°¿ voltage or í µí°¿ 0 are lattice constants when the voltage is applied or is not applied, respectively. The linear relationship between applied electric field and the lattice strain was observed in Fig. 3. The d33 was estimated by using the slope of this response without removing substrates by (3.1). Next, the electromechanical coupling coefficient kt 2 were estimated by (4). The elastic stiffness c E predicted by DFT [9] and the dielectric constants reported by Yanagitani et al. [10] were used. Here, the elastic stiffness c E were ...
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... High overtone bulk acoustic resonator (HBAR) devices, without the requirement of a suspended film structure, are widely used to estimate the piezoelectric response and electromechanical coupling coefficient with the advantage of a simplified fabrication process [32]. The fabrication process of Al1−xScxN HBAR devices with x = 0 and 10% is shown in Figure 3. ...
Aluminum scandium nitride (Al1−xScxN) film has drawn considerable attention owing to its enhanced piezoelectric response for micro-electromechanical system (MEMS) applications. Understanding the fundamentals of piezoelectricity would require a precise characterization of the piezoelectric coefficient, which is also crucial for MEMS device design. In this study, we proposed an in situ method based on a synchrotron X-ray diffraction (XRD) system to characterize the longitudinal piezoelectric constant d33 of Al1−xScxN film. The measurement results quantitatively demonstrated the piezoelectric effect of Al1−xScxN films by lattice spacing variation upon applied external voltage. The as-extracted d33 had a reasonable accuracy compared with the conventional high over-tone bulk acoustic resonators (HBAR) devices and Berlincourt methods. It was also found that the substrate clamping effect, leading to underestimation of d33 from in situ synchrotron XRD measurement while overestimation using Berlincourt method, should be thoroughly corrected in the data extraction process. The d33 of AlN and Al0.9Sc0.1N obtained by synchronous XRD method were 4.76 pC/N and 7.79 pC/N, respectively, matching well with traditional HBAR and Berlincourt methods. Our findings prove the in situ synchrotron XRD measurement as an effective method for precise piezoelectric coefficient d33 characterization.
