Evaluation of the methods for determining K2t of piezoelectric thin films deposited on substrate plates

Abstract

The validity and reliability of three recently developed methods to determine the electromechanical coupling coefficient k of a piezoelectric thin film deposited on a substrate were evaluated by numerical simulations. The simulation results indicate when the related parameters except k of the composite resonator are known, an “input impedance data fitting method” is an accurate and reliable method for extracting the k. However, when the mechanical losses in the film and substrate are unknown, but larger than 0.1%, this method is not valid. When the related parameters of the composite resonator (except k, and the mechanical losses in the film and substrate) are known, moreover, if the mechanical loss in the film is less than 5%, and a low-loss substrate is chosen, an “effective coupling factor fitting method” and a “direct method” can be used to extract the k in a valid and reliable manner

Key Words:

• Piezoelectric thin film
• electromechanical coupling coefficient
• composite transducer