Electromechanical Properties of Ferroelectric Thin Films for Piezoelectric MEMS Applications
Piezoelectric microelectromechanical systems (MEMS) employing ferrroelectric thin films have been extensively studied. In this paper, materials issues of the piezoeletric films are presented. Temperature dependence of the electrical and electromechanical properties of Pb(ZrxTi1-x)O3 (PZT, x= 0.3, 0.52, and 0.7) thin films were measured using scanning probe microscopy in the temperature range from -100°C to 150°C. The field-induced displacement increased with increase of the temperature; however, their temperature dependence was relatively small, compared with that reported on bulk PZT ceramics. Thus far, the use of PZT film has been most widely studied for MEMS applications. However, the lead toxicity associated with PZT and other lead oxide-based ferroelectrics is problematic. Therefore, properties of the lead-free thin film piezoelectrics are also described in this paper. As candidate for the lead-free piezoelectrics, Bi4-xNdxTi3O12 (BNT) and Ba(Zr0.2Ti0.8)O3 (BZT) thin films are chosen. BNT and BZT films prepared by chemical solution deposition exhibit field-induced strain corresponding to 38 pm/V and 35 pm/V, respectively.
H. Maiwa "Electromechanical Properties of Ferroelectric Thin Films for Piezoelectric MEMS Applications", Advances in Science and Technology, Vol. 45, pp. 2422-2431, 2006