Microfabrication and characterization of PVDF copolymer thin films suitable for integrating with optical microsystems

In the emerging field of Micro Electro Mechanical Systems (MEMS) silicon continues to be the best material to integrate with mechanical and electrical miniature systems such as microsensors and microactuators that use various schemes of sensing and actuation. The functionality of these systems may be enhanced from extended type of materials with enhanced sensitivity and improved actuation. The integration of piezoelectric materials in MEMS facilitates the functionality of the devices. PVDF (Polyvinylidene fluoride) and its copolymers in the domain of piezoelectric materials have always been upfront to integrate with MEMS, in particular, copolymers of PVDF possess a much enhanced material properties and can eventually deliver better performance than PVDF homopolymer. The application of copolymers extends to all classes of miniaturized systems such as optical microsystems, sensors, actuators etc. In thin film technology, it is very important to have a better understanding of the crystal structure and material properties of thin films.; In the present work microfabrication and characterization of P(VDF-TrFE) copolymer thin films are carried out. Various deposition techniques for PVDF thin films are presented and spin coating technique is finally adopted for microfabrication of PVDF copolymer thin films due to its advantages. Further spinning characterization of PVDF copolymer thin films are presented. An optimized set of spin parameters are found in order to develop a uniformly deposited PVDF copolymer thin films. In the current work, polarization of the films is performed through step-wise poling method. A simple experimental setup for stepwise poling method is presented. The main aspect of the present work is focused on the material characterization of the microfabricated PVDF copolymer thin films through "Fourier Transform Infrared Spectroscopy" (FTIR). An in-depth FTIR analysis on the effect of annealing PVDF copolymer thin films is presented and the analysis is extended through the study on the variation of the significant optical parameters such as absorbance and transmittance spectra in the infrared region. The study focuses on the variation of the spectra in the piezoelectric phase of the thin films. Further, the effect of polarization (poling ) of PVDF copolymer thin films on the absorbance and transmittance spectra is also presented, FTIR analysis is further extended through comparison of the spectra of the microfabricated PVDF copolymer thin films with the available commercial PVDF thin films.; In the present work, the mechanical properties of the spin coated PVDF copolymer thin are characterized through the measurement of piezoelectric constant, d31 for the considered geometry of PVDF copolymer thin films. The results are compared with the measured piezoelectric constant of commercial PVDF thin film. Finally a novel variable optical attenuator (VOA) through piezoelectric actuation is presented. The design of the VOA using PVDF copolymer thin films is discussed and the optical attenuation properties of the VOA are analyzed.