| AVS 60th International Symposium and Exhibition | |
| MEMS and NEMS | Tuesday Sessions |
| Session MN+NS-TuM |
| Session: | Micro and Nano Systems based on Carbon and Piezoelectric Materials |
| Presenter: | S. Trolier-McKinstry, Penn State University |
| Correspondent: | Click to Email |
Piezoelectric microelectromechanical systems offer an interesting way of achieving sensing and actuating capabilities on-chip, at voltage levels that are compatible with many CMOS devices. As a result, there is a burgeoning interest in exploiting films that can produce large strains over a wide range in length scales. This talk will address the use of perovskite thin films (especially PbZr0.52Ti0.48)O3, PZT, and 70PbMg1/3Nb2/3O3 – 30PbTiO3, PMN-PT) in applications where the critical dimensions range from tens of nm to meters. Particular attention will be placed on 1) use of actuators to correct figure errors in next-generation X-ray space telescopes and 2) a potential CMOS – replacement technology for computation which hinges on use of a piezoelectric thin film to drive a resistance change in a piezoresistor.
On the extreme upper end are large area devices for applications such as adaptive optics. In this case, the piezoelectric film can be used to produce local deformation of a mirror surface, in order to correct figure errors associated with fabrication of the component or to correct for atmospheric distortion. For example, should a mission such as Gen-X be flown, it would require up to 10,000 m2 of actuatable optics in order to correct the figures of the nested hyperboloid reflecting segments. The piezoelectric layers were deposited by sputtering; the best insulation properties were obtained in films that avoided lead excess phases at the grain boundaries. Measurements of the influence function resulting from actuation of one or more of the piezoelectric cells (to change the local curvature of the substrate) demonstrate that such adjustable optics should be able to increase the resolution of X-ray telescopes by an order of magnitude.
A fast, low power, transistor-type switching device has been proposed in which piezoelectric and piezoresistive materials are employed in a stacked sandwich structure of nanometer dimension. Of particular interest to this program is the functionality of the high aspect ratio piezoelectric 70Pb(Mg1/3Nb2/3)O3-30PbTiO3 (PMN-PT) component. PMN-PT films of 0.3 – 1.1 microns in thickness were made by a 2MOE solvent sol-gel route. These films were phase pure by XRD with dielectric constants exceeding 1500 and loss tangents of approximately 0.05. The films showed slim hysteresis loops with remanent polarizations of about 8 μC/cm2 and breakdown field > 1.5 MV/cm. The films exhibited large signal strain > 1% with d33,f of approximately 80 pm/V. It has been found that laterally patterning the piezoelectric layer in this case produces an increased dielectric response indicative of a reduction in substrate-induced clamping.