Comprehensive characterization of PVDF-TrFE thin films for microelectromechanical system applications

Abstract

This paper presents a comprehensive characterization of a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) thin film with 75/25 molar ratio for piezoelectric MEMS applications. PVDF-TrFE film was deposited on a silicon substrate using spin coating, and electrodes were formed using sputtering. Dielectric constant and dielectric loss factor were measured at different frequencies. Frequency and temperature dependence of the ferroelectric response was examined to investigate required poling conditions and maximum operating temperature. The lower limit for the coercive field was measured as 55 V/μm at room temperature. Coercive field decreased with temperature with a slope of −0.1 V/μm K, and ferroelectric to paraelectric transition occurred between 100 and 108 °C. Piezoelectric displacement measurements were performed using an atomic force microscope based method. Average value of the effective piezoelectric d33 coefficient was measured as −23.9 pm/V. No degradation was observed in this value after 2 × 105 unipolar excitation cycles. On the other hand, significant fatigue was observed in the piezoelectric response due to polarization switching; 1.8 × 105 cycles caused an average reduction of 33% in the effective d33. Presented data corroborates with the previous studies in the literature and can be used in the design of PVDF-TrFE based MEMS devices utilizing its dielectric, ferroelectric, and piezoelectric properties.