Unusual growth of polycrystalline oxide film induced by negative ion bombardment in the capacitively coupled plasma deposition

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Polarization control of ScAlN, ZnO and PbTiO₃ piezoelectric films: application to polarization-inverted multilayer bulk acoustic wave and surface acoustic wave devices

Abstract Polarization-inverted multilayers are promising for application in bulk acoustic wave (BAW) resonators, BAW transformers, surface acoustic wave (SAW) devices and nonlinear optics crystals (NLOs). However, is difficult to obtain a polarization-inverted multilayer by a conventional polarization control technique using a buffer layer. Recently developed ion beam-induced polarization inversion film growth is attractive for multilayer fabrication. Low-energy ion beam irradiation (several hundred electron volts) during film growth enables the growth of polarization-inverted (0001)/(000 1 ¯ ) c-axis normal ZnO, AlN and ScAlN piezoelectric films. These structures excite a thickness extensional mode (longitudinal wave). In contrast, high-energy ion beam irradiation (300–3000 eV) induces c-axis parallel film growth which allows the fabrication of c-axis horizontal inversion ZnO and AlN multilayers. These structures are suitable for thickness shear mode (TSM) film bulk acoustic resonators (FBARs), TSM liquid sensors and out-of-plane NLOs. This review introduces the unusual polarization inversion film growth induced by ion beams and its applications. On the other hand, a (001)/(00 1 ¯ ) polarization-inverted layer can be obtained using ferroelectric films. This paper also provides the result of external electric field-induced polarization inversion of PbTiO3 epitaxial films.</jats:p

Oblique Incidence Ultrasonic Reflectometry Device Based on c-axis Tilted ScAlN Films for Evaluating Viscoelastic Properties of Liquids Above 100 MHz

Abstract Ultrasound-based evaluation of fluid properties allows for real-time measurement of small amounts of liquid samples. The ultrasonic reflection method is used to obtain the complex reflection coefficient, which can be used to evaluate the viscoelastic properties of liquids. However, this method has not been used with shear waves at frequencies above 100 MHz because shear-mode piezoelectric films are difficult to obtain at such frequencies. We propose using the oblique incidence reflectometry with quasi-shear waves excited by c-axis tilted scandium aluminum nitride (ScAlN) thin films to realize high-sensitivity evaluation of the viscoelastic properties of liquids in the above 100 MHz. In experiments, the shear elasticity and shear viscosity of glycerin solutions were estimated from their complex reflection coefficients.</jats:p