Cantilever resonator based on the electrostriction effect in Gd-doped ceria

Thin films of Ce_0.8Gd_0.2O_1.9, which have recently been shown to demonstrate giant electrostriction, are proposed as the active material for miniature cantilever resonators and actuators. In the absence of strain, these films have an electrostriction coefficient within the range of 2-10 kPa/(kV/cm)², as compared with the somewhat larger values for the best commercial electrostrictors (e.g. PbMn_1/3Nb _2/3O₃, 62 kPa/(kV/cm)². At the same time, Ce_0.8Gd_0.2O_1.9 films can generate stress >70 MPa which is competitive with materials currently in use and only limited by the strength of the film-substrate interface. In this report, we investigate two aspects of the practical application of Ce_0.8Gd_0.2O _1.9 as a resonator: the fabrication conditions and the frequency dependence of the electrostrictive behavior. We show that the films can display electromechanical response with frequencies up to 6 kHz. With respect to fabrication, we show that Ce_0.8Gd_0.2O_1.9 films have a number of technological advantages when compared to the lead titanate based materials currently in use: (a) they can be deposited on a variety of metal contacts and substrates, including silicon; (b) they do not require high temperature processing; and (c) because Ce_0.8Gd_0.2O _1.9 has cubic symmetry, it can in principle be used as a polycrystalline film with arbitrary texture and does not require poling. In addition, neither Ce nor Gd nor their oxides are toxic; the oxides have very low vapor pressure; and the cations, being highly charged do not diffuse into Si. Consequently, Ce_0.8Gd_0.2O_1.9 films may be readily and advantageously integrated into existing semiconductor fabrication technologies.