Characterisation of piezoelectric thin films by areal laser scanning

Piezoelectric thin films have great potential as transducer materials for many micro electromechanical systems (MEMS). An efficient characterisation technology for the piezoelectric properties of the thin films is becoming particularly essential for both fundamental materials research and practical applications. However, the variation among the reported data in the literature for piezoelectric films is significantly large as no widely accepted standard measurement technique has been popularly used. In this paper, we report the characterization method and results of our ferroelectric lead zirconate titanate (PZT) thin film samples by areal laser scanning. It is demonstrated that the monitoring of the vibration of the surface area, rather than a single point as reported previously, could result in much more comprehensive and accurate information about the piezoelectric performance of the films. The longitudinal piezoelectric dilatation data of the ferroelectric films are acquired at different frequencies and voltages. A theoretical analysis is given to further clarify the relationship between the detected vibration magnitude and the piezoelectric coefficient. The advantages of using the laser scanning vibrometer for characterising piezoelectric thin films are discussed in comparison with other methods. (C) 2004 Elsevier B.V. All rights reserved.