Materials development for thin film actuators

Abstract

In the development of microsystems, actuators are required which can be triggered in various different ways. The actuating principles to be used are magnetostriction, the inverse piezoelectric effect, the shape memory effect, and the bimetallic effect. The variables triggered in these cases are magnetic fields, electric fields, or temperature changes. Thin film actuators are of special interest for the development of microsystems, as they can be easily scaled down to the μm-range and as their manufacturing is compatible to microsystem fabrication processes. The common property of these materials is their ability to transform electrical into mechanical energy by the effects mentioned above. Of special interest are magnetostrictive or piezoelectric materials as they allow energy transformation in both directions. These inverse effects can therefore be employed as sensoric mechanism for mechanical sensors (e.g. for stress, pressure, torque) as well. The report contains a discussion of various PVD techniques sucessfully used for producing magnetostrictive films (TbFe, TbDyFe, SmFe), piezoelectric films (PbtiO3, ZnO, AlN), shape memory films (TiNi, TiNiPd, TiPd) and bimetallic film composites (e.g. FeNi20Mn6-FeNi42). The properties of these layers are presented and compared. Possible applications and future development are outlined.