New Methods of Measuring a Key Elastic-Piezoelectric Constant of Thin Films

F. J. von Preissig, H. Zeng, and E. S. Kim

To be pesented at: ASME International Mechanical Engineering Congress and Exhibition (IMECE) Atlanta, GA, November 18-22. 1996 Symposium on Mechanics in MEMS

Microelectromechanical devices that contain piezoelectric thin films that serve as electrical-to-mechanical transducers (actuators) or mechanical- to-electrical transducers (sensors) are receiving increasing attention. The efficiency of transduction usually depends largely on the composite elastic- piezoelectric constant d(sub 31)/(s^E(sub 11)+s^E(sub 12)) of the piezoelectric film. Two new methods for measuring this constant, based on the same piezoelectric device, have been developed. The analytical theory behind these methods has been worked out in detail. One method involves the measurement of small mechanical displacements. Its application to a device containing polycrystalline ZnO yielded a value of 0.13 C/m^2 for the constant. The other method requires only electrical and simple geometric measurements. Its experimental implementation has not yet been completed.