Takahiko Yanagitani

Distribution of hydroxyapatite crystallite orientation and ultrasonic wave velocity in ring-shaped cortical bone of bovine femur

At the nanoscopic level, bone consists of calcium phosphate, which forms incomplete hydroxyapatite (HAp) crystals. The preferred orientation of the c-axis of HAp crystallites induces anisotropy and inhomogeneity of elastic properties in bone. In this study, the effect of the preferred orientation of HAp crystallites on the spatial distribution of ultrasonic wave velocity was experimentally investigated, considering bone mineral density (BMD) and microstructure. Three ring-shaped cortical bone samples were made from a 36-month-old bovine femur. Longitudinal wave velocity was measured by a conventional ultrasonic pulse system, using self-made polyvinylidene fluoride transducers. The integrated intensity of the (0002) peak obtained using X-ray diffraction was estimated to evaluate the amount of preferred orientation. The velocity distribution pattern was similar to the distribution of integrated intensity of (0002). The effect of the preferred orientation of HAp crystallites on velocity was clearly observed in the plexiform structure, despite the fact that the BMD value was almost independent of the preferred orientation of HAp crystallites. Velocity measurement of cortical bone can reveal information about HAp crystallite orientation.

P3H-3 Thin Film Stack Transducer for Simultaneous Generation of Longitudinal and Shear Waves at Same Frequency

It is difficult to generate longitudinal and shear bulk waves simultaneously at same frequency. In this study, we propose new film stack transducer structure consisting of two layers of c-axis 23deg-tilted ZnO films. The upper layer and lower layer in the stack have same thicknesses, and the c-axis tilt direction in the both layers are symmetric with respect to the film surface normal. This film stack transducers were fabricated on silica glass substrate by using RF magnetron sputtering technique. Crystallographic properties of the transducer were determined by XRD pole figure analysis. Detailed conversion loss characteristics of the transducer were also discussed. Simultaneous generation of both waves at same frequency was then experimentally demonstrated in the VHF range. We also included thin film fabrication technique for obtaining two layers of c-axis-tilted ZnO films with good crystalline orientation.

4E-4 Propagation Characteristics of SH-SAW in (1120) ZnO Layer/Silica Glass Substrate Structures

A (1120) textured ZnO film can excite SH-SAW. Therefore, the film on various substrates is an attractive option for fabricating the SH-SAW device on a silicon IC, and the device on a curved surface. In this report, the electromechanical coupling coefficients (K1) in the ZnO (0deg, 90deg, psi) film/silica glass substrate structures were theoretically estimated. The theoretical results showed that the IDT electrode/ZnO (0deg, 90deg, 55deg) film/silica glass substrate structure had a relatively large K2 value of 3.4 % at H/lambda=0.21. This structure was then fabricated using RF magnetron sputtering technique. The experimental results clearly demonstrated SH-SAW excitation in the structure.

P1J-1 Temperature Characteristics of Pure Shear Mode FBARs Consisting of (1120) Textured ZnO Films

Thickness extensional mode FBAR consisting of (0001) textured ZnO films and pure thickness shear mode FBAR consisting of (112macr0) textured ZnO films were fabricated. Temperature coefficients of frequency (TCF) of these FBARs were measured in the temperature range of 10-60 degC. In both of the resonators, the parallel resonant frequencies varied linearly with temperature. The TCF were determined as -63.1 [ppm/degC] for thickness extensional mode resonator and -34.7 [ppm/degC] for pure-shear mode resonator

P1G-5 Ion Beam Sputter-Deposited ZnO Thin Film for Broadband Shear Wave Excitation in the GHz Range

In-plane and out-of-plane oriented (112macr0) ZnO thin films are attractive for shear wave excitation in the GHz range. It is proposed here that highly oriented and submicron-thick (112macr0) ZnO thin films can be fabricated using ion beam sputter-deposition system with grazing incidence to the substrate surface. This (112macr0) texture formation cannot only be attributed to the well-known ion channeling effect or to the self-shadowing effect since the ion beam incidence direction in the system does not correspond to the ion channeling direction of the ZnO film (the [101macr0] or [112macr0] direction). Full-width-at-half-maximum (FWHM) values of the phi-scan and psi-scan profile curves of the (112macr2) X-ray diffraction poles were measured to be 5deg and 28deg, respectively. A shear-wave transducer with a 0.9-mum-thick film exhibited an untuned one-way conversion loss of less than 20 dB at 1 - 2 GHz and a 3 dB-fractional bandwidth of 100%, without any longitudinal wave excitation.