Use of epitaxial PZT thin films for La2/3Sr1/3MnO3based MEMs devices on SrTiO3/Si

Abstract

Lead zirconate titanate Pb(Zr,Ti)O3 (PZT) is a well know ferroelectric material with excellent piezoelectric properties, namely large piezoelectric coefficients, low leakage current and reliable performance, which makes it very suitable as an actuator material in Micro-ElectroMechanical Systems (MEMS). The performance of piezoelectric MEMS is, however, strongly dependent on the film quality. In the present work, the epitaxial growth of PZT is desired as it can help to reduce high-frequency losses, to allow for larger electromechanical coupling and to increase the final device sensitivity. We used an epitaxially grown conductive oxide bottom electrode, namely 45 nm thick La2/3Sr1/3MnO3 (LSMO) films, deposited on SrTiO3 buffered (001) silicon substrates using a combination of pulsed laser deposition and reactive molecular beam epitaxy techniques. The 500 nm thick c-axis oriented PZT layers were deposited at 600°C by magnetron sputtering on the LSMO films on STO/Si (001). The piezoelectric and ferroelectric properties of the PZT layers were studied by PiezoForce Microscopy on as-grown PZT films and Polarization versus Electric field measurements on samples covered with Pt top electrodes. The PZT films exhibited good piezoelectric and ferroelectric properties with a remanent polarization higher than 20 µC·cm−2, which makes them suitable for the fabrication of piezoelectric MEMS based on doubly-clamped LSMO suspended structures.