Patent ID: 9450171
Filing Date: 2016-09-20
CPC Classification: G11B,H01L

Claim Text:
1. A thin film piezoelectric element comprising: a substrate; and a piezoelectric thin film stack formed on the substrate, and the piezoelectric thin film stack comprising a top electrode layer, a bottom electrode layer and a piezoelectric layer sandwiched between the top electrode layer and the bottom electrode layer, wherein the piezoelectric layer comprises a first piezoelectric layer and a second piezoelectric layer whose compositions have different phase structures, the second piezoelectric layer is formed directly on top of the first piezoelectric layer, the top electrode layer is formed directly on top of the second piezoelectric layer, and the bottom electrode layer is formed directly below the first piezoelectric layer, wherein the piezoelectric layer comprising the first and second piezoelectric layers is formed to have a compositional constitution and physical structure that ensures that (a) stroke of the thin film piezoelectric element is progressively increasable by increasing AC voltage provided to the thin film piezoelectric element up to about 50 volts, at which point depolarization occurs, and (b) in use, the thin film piezoelectric element has a depoling voltage change and a polarization change of no more than +/−10% over a temperature range of −40° C. to 125° C.