ABSTRACT
In-plane unstrained single-c-domain/single-crystal thin films of PZT-based ternary ferroelectric perovskite, ξPb(Mn,Nb)O3-(1 - ξ)PZT, were grown on SrRuO(3)/Pt/MgO substrates using magnetron sputtering followed by quenching. The sputtered unstrained thin films exhibit unique ferroelectric properties: high coercive field, Ec > 180 kV/cm, large remanent polarization, P(r) = 100 µC/cm(2), small relative dielectric constants, ε* = 100 to 150, high Curie temperature, Tc = ~600 °C, and bulk-like large transverse piezoelectric constants, e31,f = -12.0 C/m(2) for PZT(48/52) at ξ = 0.06. The unstrained thin films are an ideal structure to extract the bulk ferroelectric properties. Their micro-structures and ferroelectric properties are discussed in relation to the potential applications for piezoelectric MEMS.
ABSTRACT
A highly sensitive piezoelectric ultrasonic micro-sensor with a grooved multilayer membrane was developed by a Si-based MEMS technique. The groove was located at one-quarter of the distance away from the edge of the membrane and opened into piezoelectric layer. The piezoelectric layer Pb(Zr,Ti)O(3) (PZT) was 2.2 microm thick and was prepared by a sol-gel method. The prepared PZT film was pure perovskite and showed a highly (100) textured structure. The sensitivity of the fabricated piezoelectric ultrasonic sensor without the groove structure was 100 microV/Pa. In comparison, the sensitivity of the ultrasonic sensor with the groove structure was about 500 microV/Pa, which is 5 times that without the groove structure. The diaphragm having grooves showed a corrugate-like structure that was formed by residual stress. The high sensitivity of the membrane with the grooved diaphragm is considered to relate to the corrugate-like structure.
