Ferroelectric films and micro devices.

Abstract

The study of microelectromechanical systems (MEMS) has of late opened up significant new opportunities for miniaturized mechanical devices based on thin film materials and silicon technology. Their functionality can be increased by joining many elements on a small space. Infrared detector arrays, high-frequency ultrasonic imaging arrays and cantilever arrays for mass storage applications are examples of such improvement. An important family of functional materials is ferroelectrics, or more generally polar materials. Their piezoelectricity can be used in sensors, actuators and transducers, while pyroelectricity is used in infrared detectors. This paper deals with the preparation and characterization of ferroelectric thin films for MEMS applications. Emphasis is laid on lead zirconate titanate (PZT) and lead calcium titanate (PCT). Sol gel technique for ferroelectric film deposition is considered in detail. Thin films of (Pb,La)(Zr,Ti)O3 have been deposited by sol gel method on a variety of substrates. Attempts have been made to crystallize the thin films at as low a processing temperature as possible. The properties studied include dielectric measurements and hysteresis. Thin films of calcium-modified lead titanate (PCT) were also prepared by the sol gel technique and their pyroelectric characteristics were studied for use in infrared detectors.film was coated. These results show that the crystalline quality and deposition rate can be controlled over a wide range by this method.