Improvement of c-Axis Parallel Orientaition of ZnO film on Silica Glass Pipes with Various Diameters for SH-SAW Pipe Sensor

Shear horizontal surface acoustic wave (SH-SAW) sensors have been studied for measurements of liquid properties. The long-distance propagation of SH-SAW with multiple wave roundtrips on a pipe surface improve the measurement sensitivity. c-Axis parallel oriented ZnO films can excite the SH-SAW and be grown on a curved surface by a sputtering deposition. In this study, the ZnO film growths on pipe surfaces with various pipe diameters were demonstrated. The c-axis parallel oriented ZnO film with high orientation was only obtained on the pipe surface facing the sputtering target plane. A slit which limits the deposition area and an automatic rotation system of the pipe were effective for the uniform film growth on the entire pipe surface. This film/pipe substrate structure is a good candidate for the SH-SAW sensor with high sensitivity.