Piezoelectric PZT MEMS technologies for small-scale robotics and RF applications
- PDF / 1,278,704 Bytes
- 9 Pages / 585 x 783 pts Page_size
- 70 Downloads / 243 Views
Introduction Lead zirconate titanate (PZT) is a versatile material that possesses piezoelectric, pyroelectric, ferroelectric, and electrostrictive material properties. Since the early development of PZT in the 1950s, the material has become pervasive in a variety of bulk actuator applications and is used in low cost ceramic filters due to its piezoelectric properties.1,2 It has been explored for infrared radiation (IR) detectors and imagers by utilizing its pyroelectric properties.3 Commercially available ferroelectric random access memory (FRAM) technology based on thinfilm PZT exploits its ferroelectric properties for non-volatile memory.4–7 However, it is the strong piezoelectric properties of thin-film PZT as exploited in piezoelectric MEMS (piezo MEMS) devices that enable exciting new application spaces such as millimeter-scale robotics. Purely polar piezoelectric (non-ferroelectric) materials such as AlN and ZnO have been extensively explored in MEMS for sensor and resonator applications8 (as described in the
article by Piazza et al. in this issue). Both materials are directly complementary metal oxide semiconductor (CMOS) process compatible and possess low dielectric constants and low material losses, but modest piezoelectric properties. The commercially successful film bulk acoustic resonator filter technology that resides in most cell phones today relies on thin-film AlN as the piezoelectric transducer material.9,10 In contrast, PZT materials, especially near the morphotropic phase boundary composition (Zr/Ti = 52/48), where the phase transitions between the tetragonal and rhombohedral ferroelectric phases possess higher dielectric constants and higher mechanical and dielectric losses, also exhibit piezoelectric coefficients and electromechanical coupling factors that are more than an order of magnitude larger than those of the non-ferroelectric materials.11,12 Randomly oriented PZT films exhibit effective thin-film, transverse piezoelectric coefficients e31,f in the range of –6 to –8 C/m2,10 while 001 textured films with minimal Zr/Ti gradients through the film thickness have recently shown values as high as –18 C/m2.13
Jeffrey S. Pulskamp, US Army Research Laboratory, Adelphi, MD; [email protected] Ronald G. Polcawich, US Army Research Laboratory, Adelphi, MD; [email protected] Ryan Q. Rudy, University of Maryland, College Park; [email protected] Sarah S. Bedair, US Army Research Laboratory, Adelphi, MD; [email protected] Robert M. Proie, US Army Research Laboratory, Adelphi, MD; [email protected] Tony Ivanov, US Army Research Laboratory, Adelphi, MD Gabriel L. Smith, US Army Research Laboratory, Adelphi, MD; [email protected] DOI: 10.1557/mrs.2012.269
1062
MRS BULLETIN • VOLUME 37 • NOVEMBER 2012 • www.mrs.org/bulletin
© 2012 Materials Research Society
PIEZOELECTRIC PZT MEMS TECHNOLOGIES FOR SMALL-SCALE ROBOTICS AND RF APPLICATIONS
Piezoelectric actuator properties scale favorably at micron-scale dimensions; actuator force scales with thickness, while
Data Loading...
