title: Fabrication of broadband poly(vinylidene difluoride-trifluroethylene) line-focus ultrasonic transducers for surface acoustic wave measurements of anisotropy of a (100) silicon wafer.
abstract: This paper investigates a new method for fabrication of broadband line-focus ultrasonic transducers by sol-gel spin-coating the poly(vinylidene difluoride-trifluroethylene) [P(VDF-TrFE)] copolymer film on a concave fine-polished beryllium copper backing. The ferroelectric hysteresis loops of the P(VDF-TrFE) films spin-coated from different molar ratios of VDF/TrFE, 77/23 and 55/45, were measured to select the better mixture. Owing to the better acoustic matching to water, compared with lead zirconate titanate (PZT), the fabricated transducers show relatively wide bandwidth of approximately 50 MHz with high central frequency of 60 MHz obtained at the focal plane when a fused-quartz acts as a reflecting target. Each one of the two finished transducers has a focal length of 5mm and a full aperture angle of 90°. After applying the specially developed digital signal processing algorithm to the defocusing experiment data, which is called V(f,z) analysis method based on two-dimensional fast Fourier transform (2-D FFT), the operating frequency can extend from several MHz to over 90 MHz. Surface acoustic wave (SAW) velocities of a typical (100) silicon wafer was measured along various directions between [100] and [010] to represent the anisotropic features.
authors.affiliation: College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Lu
authors.forename: Cunfu
authors.initials: C
authors.lastname: He
authors.forename: Guorong
authors.initials: G
authors.lastname: Song
authors.forename: Bin
authors.initials: B
authors.lastname: Wu
authors.forename: Cheng-Hsien
authors.initials: CH
authors.lastname: Chung
authors.forename: Yung-Chun
authors.initials: YC
authors.lastname: Lee
mesh_terms: D054459:Elasticity Imaging Techniques / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008422:Materials Testing / Q000295:instrumentation; D008567:Membranes, Artificial; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*; D011145:Polyvinyls / Q000737:chemistry*; D012825:Silicon / Q000032:analysis / Q000737:chemistry*; D013016:Sound; D014159:Transducers
chemical_list: D008567:Membranes, Artificial; D011145:Polyvinyls; C073666:vinylidene fluoride-trifluoroethylene copolymer; D012825:Silicon
keywords: Broadband line-focus transducer; Ferroelectric hysteresis loop; P(VDF-TrFE) film; Surface acoustic wave; V(f,z) analysis method