Giant piezoelectricity in PMN-PT thin films: Beyond PZT

Microelectromechanical systems (MEMS) incorporating piezoelectric layers provide active transduction between electrical and mechanical energy, which enables highly sensitive sensors and low-voltage driven actuators surpassing the passive operation of electrostatic MEMS. Several different piezoelectric materials have been successfully integrated into MEMS structures, most notably Pb(Zr,Ti)O-3. Piezoelectric materials with larger piezoelectric response, such as the relaxor ferroelectric Pb(Mg1/3Nb2/3)O-3-PbTiO3 (PMN-PT), would enable further miniaturization. However, this has long been hampered by the difficulties in the synthesis of these materials. This article reviews recent successes not only in synthesizing high-quality epitaxial PMN-PT heterostructures on Si, but also in fabricating PMN-PT microcantilevers, which retain the piezoelectric properties of bulk PMN-PT single crystals. These epitaxial heterostructures provide a platform to build MEMS and nanoelectromechanical system devices that function with large displacement at low drive voltages, such as ultrasound medical imagers, micro-fluidic control, piezotronics, and energy harvesting.