Minh Duc Nguyen
University of Twente, The Netherlands
Title: Control of piezoelectric properties of PZT-based ferroelectric thin films on silicon through the crystal growth for mass-sensor and actuator applications
Biography
Biography: Minh Duc Nguyen
Abstract
Ferroelectric oxides, such as Pb(Zr0.52Ti0.48)O3 (PZT), are very useful for electronic and photonic devices, as well as piezomechanical actuators and sensors. The ferro- and piezo-electric properties are strongly related to the crystal orientation as well as the crystal growth of the epitaxial PZT thin films. Successful integration of these devices into silicon technology is therefore not only dependent on the ability of crystal growth on silicon substrates, but also the control of the crystallographic orientation of the deposited PZT thin ï¬lm. In this study, the all-oxide piezoelectric stacks (PZT thin ï¬lms are sandwiched between oxide-electrodes) were grown on buffer-layers/silicon substrates using pulsed laser deposition. The microcantilever structures (length: 400 µm and width: 100 µm) consisting of a piezoelectric stack (electrode/PZT/electrode) grown on a seed-layer buffered 10-µm thick Si supporting beam were then fabricated by backside etching of a silicon-on-insulator wafer. The piezoelectric measurements show that the (110)-oriented PZT films with columnar grain structure have a higher longitudinal piezoelectric coefficient d33,f but smaller transverse piezoelectric coefficient d31,f of the (001)-oriented films with dense structure or without the clear columnar growth structure. This finding indicates that the piezoelectric properties can be changed by changing the density of the PZT. It is very important for choosing the proper film growth orientation for specific applications which require either a large in-plane (such as piezoelectric micro-machined ultrasonic transducers, micro-diaphragms and energy harvester) or out-of-plane (such as mirror structure for ultraviolet wavelengths) piezoelectric displacement.