Piezoelectric thin film

This approach can be generalized to account for more complex geometrical arrangements of the layers or for other material symmetries. The essential features of the approach are the limitation to small deflections and the translational invariance of the configuration in any direction parallel to the substrate midplane. If the substrate is absent, that is, if hs/hi — 1, the role played by the substrate midplane in the above discussion is naturally assumed by the plane face 0 3 = 0 of the remaining film. 

Piezoelectricity is a physical effect exhibited by crystals that are electrically neutral, but that do not have a center of reflective symmetry in crystal structure. The essential property of a point of reflective symmetry is that for each atomic position in the crystal lattice there is a matching atomic position at a point that is directly opposite the first with respect to the point of symmetry this second position is at a same distance from the point of symmetry as the first. For example, the face-centered cubic structure has a point of reflective symmetry at the geometrical center of the unit cell whereas the cubic zinc blende structure does not have a center of symmetry. 

When a stress is applied to such a crystal, it may become electrically polarized as a result of a charge separation on the atomic level, leaving unbalanced net charges of opposite sign on opposite faces of the crystal. A closely related phenomenon, which is known as the piezoelectric effect, is the production of mechanical strain when such a crystal is subjected to 

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Cui, T. Markus, D. Zurn, S. Polla, D. L. 2004. Piezoelectric thin films formed by MOD on cantilever beams for microsensors and actuators. Microsystem Tech. 10 1432-1858. 

In many microelectromechanical systems (mems) based on piezoelectric thin films, flexure is deliberately used to amplify the available displacements (or alternatively to increase the sensitivity of a sensor). For simplicity (and to keep poling and actuation voltages low), films are often poled and driven by electrodes at the top and bottom surfaces. As a result, the critical piezoelectric coefficient is often e31 j, rather than d33j [24], For the direct effect, the effective film coefficient, e3ij can be defined by... 

While a thin transduction layer below and/or above the input and output transducers must be piezoelectric, there is no such restriction upon the balance of the substrate. A piezoelectric thin film (such as crystallographically oriented polycrystalline ZnO or AIN) can be deposited on a non-piezoelectric substrate to provide a medium for AW excitation and detection. Thus, (non-piezoelectric) silicon wafers often serve as the substrate for SAW or FPW devices, with piezoelectric transduction provided by a layer of ZnO. Note also that this transduction layer need not extend laterally past the regions in which the IDTs are defined. 

MEMS APPLICATIONS USING PIEZOELECTRIC THIN FILMS... 

S. Miyashita, M. Shinozuka, K. Sumi, M. Murai, and T. Takahashi, Piezoelectric thin film, method for producing the same, and ink jet recording head using the thin film, US Patent 6140 746, assigned to Seiko Epson Corporation (Shinjuku-Ku, JP), October 31,2000. 

Rytov SM (1956) Acoustical properties of a thinly laminated medium. Sov Phys Acoust 2 68-80 Sadat-Saleh S, Benchabane S, Baida FI, Bernal M-P, Laude V (2009) Tailoring simultaneous photonic and phononic band gaps. J Appl Phys 106 074912 Satoh Y, Nishihara T, Yokoyama T, Ueda M, Miyashita T (2005) Development of piezoelectric thin film resonator and its impact on future wireless communication systems. Jpn J Appl Phys 44(5A) 2883-2894... 

DeVoe, D. L. Piezoelectric thin film, m,icrom,echanical beam resonators. Sensors and Actuators A 88 (2001), pp. 263-272... 

Kuoni A, Holzherr R, Boillat M, de Rooij NF (2003) Pol3timide membrane with ZnO piezoelectric thin film pressure transducers as a differential pressure liquid flow sensor. J. Micromech. Microeng. 13 103-107... 

Suppose that the piezoelectric thin film is bonded to an isotropic elastic substrate that does not exhibit piezoelectric behavior. If this film-substrate system is exposed to an electric field 8, then the film material will tend to undergo the stress-free strain specified by (3.83). However, the film is constrained from deforming freely by the substrate. As a result, a stress is generated in the film, and this stress may result in a detectable curvature of the substrate. If the X3—axis is normal to the film-substrate interface then the components of mismatch strain in the film are, in reduced notation. 

Bhaskaran, M., Sriram, S.,Ruffell, S., Mitchell, A., 2011. Nanoscale characterization of energy generation from piezoelectric thin films. Adv. Funct. Mater. 21 (12), 2251-2257. 

Blattner H., Kanzig W.J., Merz W.J., Sutter H. Helv. Phys. Acta 1948 21 207 Boulton J.M., Teowee G., Bommersbach W.M., Uhlmann D.R. Second harmonic generation from sol-gel derived ferroelectric and piezoelectric thin films. In Sol-Gel Optics, vol. II, J.D. Mackenzie, ed. Proc. SPIE 1992 1758 292-303... 

Fig. 2 Example of a fiilly flexible, transparent piezoelectric thin film surface called FlexSense. The top photograph illustrates the printed piezoelectric sensor. With a sophisticated electronic readout and algorithm, the 3D shape of the surface is captured in real time (bottom photograph) (Reprinted with permission (Rendl etal. 2014))...

The statics and dynamics of microstructures are governed by the forces that create or maintain them. Rarely can the forces be measured directly. But forces between special surfaces immersed in fluid can now be accurately gauged at separations down to 0.1 nm with the direct force measurement apparatus, an ingenious combination of a differential spring, a piezoelectric crystal, an interferometer, and crossed cyhndrical surfaces covered by atomically smooth layers of cleaved mica (Figure 9.4). This recent development is finding more and more applications in research on liquid and semiliquid microstructures, thin films, and adsorbed layers. 

This system consists of a symmetrical pair of lens elements connected by a small volume of liquid. Each lens consists of a single spherical interface between the liquid and a lens rod. The lens element is formed by polishing a small concave spherical surface in the end of a sapphire rod. At the opposite end of the rod, a thin film piezoelectric transducer is centered on the axis of the lens surface. 

The nonlinear optical and dielectric properties of polymers find increasing use in devices, such as cladding and coatings for optical fibres, piezoelectric and optical fibre sensors, frequency doublers, and thin films for integrated optics applications. It is therefore important to understand the dielectric, optical and mechanical response of polymeric materials to optimize their usage. The parameters that are important to evaluate these properties of polymers are their dipole moment polarizability a, hyperpolarizabilities 0... 

Piezoelectric materials have a variety of commercial applications, and a large number of such materials are known. To examine such materials in thin-film form, highly textured crystalline thin films are likely to be needed, so microstructure control is therefore an issue. Screening approaches should be straightforward. 

The quartz oscillator coating thickness gauge (thin film controller) utilizes the piezoelectric sensitivity of a quartz oscillator (monitor crystal) to the supplied mass. This property is utilized to monitor the coating rate and final thickness during vacuum coating. 

The simple cases where one enzyme is employed afford a limited scope of potential targets. Usually two or more enzyme reactions are coupled, as exemplified by the development of a piezoelectrically-transduced biocatalytic biosensor that couples two enzyme reactions to detect glucose [492-62-6], C6H120 > (3) (13). In this biosensor a quartz radio crystal is functionalized with the enzyme glucose-6-phosphate dehydrogenase. As shown in Figure 3, a thin film of Prussian blue [14038 43-8], C18N18Fe7, is then coated onto the crystal. 

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