No abstract

Lead zirconate titanate (PZT) thin film was formed on Pt/Ta/Si3N4/Si(100) substrate at 400 °C by sputtering and then annealed at 650 °C in air. The PZT film was 1 μm thick and had dielectric permittivity of 980, loss tangent of 0.05, remanent polarization of 31 μC/cm2, and coercive field of 110 kV/cm. Piezoelectric property of the film formed on silicon cantilever was estimated from the converse effect. Poling at 5 kV/mm increased the property by a factor of 1.2 to 3.4, resulting in converse piezoelectric constant (d31) varying from −84 to −102 pC/N.

Elimination of optical and tunneling displacement sensors from the atomic force microscope ͑AFM͒ is an important breakthrough for improved performance of the AFM. The interaction of an oscillating tip and a surface has become a popular tool for obtaining information which could not be obtained by the conventional repulsive force AFM mode. In this application, lead zirconate titanate ͑PZT͒ is one of the most promising materials with large piezoelectric constants which can be used not only for detecting distortions such as the displacement detection of an AFM cantilever, but also oscillations of the cantilever. However, incorporating PZT into the microfabrication process to make the AFM cantilever has not been easily accomplished because PZT has a delicate chemical nature. We have successfully developed an AFM with a microfabricated cantilever which had a PZT thin film applied for displacement sensing. The linearity of the output signal was sufficient for displacement sensing. Images of a compact disk were obtained to assure the capability of the PZT thin film for AFM detection.

A novel process for fabricating lightweight, cellular ceramics from sols is presented. The process utilizes the rapid viscosity change during gelation to stabilize the structure of a foamed silica sol. Manipulation of gel viscosity and foaming agent concentration resulted in a minimum cell size of 90 pm at 31% density and minimum density of 17% with average cell size of 400 pm. The flexural strength compared favorably with space shuttle tiles and sintered hollow glass spheres. From -50" to 15o"C, the dielectric constant ranged from 1.51 to 1.55 for a 20% dense foam and was slightly dispersive, whereas the dielectric loss was comparable with fused silica. [