Kenzo Ohji

Electro‐optic effects of (Pb, La)(Zr, Ti)O3 thin films prepared by rf planar magnetron sputtering

Epitaxial (Pb, La)(Zr, Ti)O3 thin films were grown successfully on (0001) sapphire substrates at below 600 °C. High quadratic electro‐optic coefficient of 0.8×10−16 (m/V)2 was also obtained at 6328 A. The rf planar magnetron sputtering process improved the quality of the film, which will be suitable for thin‐film integrated optic devices.

Highly‐oriented ZnO films by rf sputtering of hemispherical electrode system

Highly oriented ZnO films (c‐axis orientation) were fabricated on glass and fused‐quartz substrates by an rf‐sputtering system with a hemispherical electrode configuration. The sputtered films show a high longitudinal mode electromechanical coupling factor, kt=0.23–0.24. Initial results suggest that the hemispherical electrode configuration may provide improved reproducibility over planar sputtering systems in the preparation of ZnO films for acoustic device applications.

Piezoelectric thin films of zinc oxide for saw devices

Abstract Fabrication processes of piezoelectric ZnO films utilizing sputtering deposition technique and properties of the sputtered films are described mainly in view of their application to surface-acoustic-wave (SAW) devices. Both polycrystalline films with c-axis orientation and single-crystal films on sapphire are treated in this paper. As for the polycrystalline films, it is emphasized that an improved sputtering system with a hemispherical electrode configuration provides excellent uniformity of film thickness and c-axis orientation. The single-crystal films have been successfully grown by conventional rf-sputtering and rf magnetron sputtering. The rf magnetron sputtering is found to be superior over the conventional method with respect to SAW properties of the films. Fundamental SAW properties have been measured for the films and the results are compared with theoretical predictions. Several SAW devices in a wide variety of operating frequency (30–2200 MHz) have been realized using the ZnO films. S...

SAW resonators using rf‐sputtered ZnO films on glass substrates

SAW resonators have been fabricated from reflection strip arrays of ZnO films on borosilicate glass substrates by rf sputtering and standard photolithographic processing. Unloaded Q values were nearly 1000 and a linear temperature coefficient of about −10 ppm/°C was obtained when operated at a frequency of 100 MHz. Achievable Q values for ZnO/glass SAW resonators at this frequency are discussed.

New sputtering system for manufacturing ZnO thin‐film SAW Devices

An improved rf sputtering system for manufacturing ZnO thin‐film devices is described. The system consists of a hemispherical electrode geometry with a ZnO center cathode and provides c axis highly oriented ZnO films onto 60 sheets of glass substrate wafers of 25 mm square in one sputtering run. The growth rate of ZnO films is 0.3–0.7 μm/h. The film thickness variations in these wafers are within ±1%. The electrical resistivity of the films ρ?106–107 Ω cm, dielectric constant e*?8.5, the electromechanical coupling in a longitudinal mode kt?0.23–0.24, in a Rayleigh mode keff?0.07–0.085 for the ZnO film thickness of 3% of the wavelength. The present system enables the manufacture of the ZnO thin‐film SAW filter with a frequency accuracy, better than ±0.1%, and a temperature stability, better than −10 ppm/°C.

Surface Wave Transducers of ZnO Films with Controlled Direction of C–axis

ZnO films for thin film surface wave transducer have been deposited by cathodic sputtering. ZnO films with c-axis normal to the film plane are produced by dc and rf sputtering from zinc metal and zinc oxide cathode, respectively, in an oxidizing atmosphere. ZnO films with c-axis in the film plane are produced by the dc sputtering with small amounts of aluminum. The rf sputtered ZnO films with c-axis normal to the film plane have high coupling factors of 0.05 to 0.75 for surface wave excitations in the ZnO film thickness of 3 to 6% of the wavelength in the plated-interdigital surface wave transducers.

Observation of Chladni Figures in Piezoelectric Ceramic Plates of Rectangular Form

Observation of the Chladni figures was made on a piezoelectric ceramic plate which may be used as a piezoelectric transformer. Many spurious vibration modes were easily excited besides the normal mode. Those spurious modes were found to be the thickness flexure mode. The position where the transformer is to be supported could be determined from the Chladni figures. The resonant frequencies of the spurious mode were in better agreement with the calculated values from the frequency equation of a rectangular beam vibration in the flexure mode rather than with those from Rayleigh-Lamb equation.