Piezoelectric actuator including X-graded TiO
In a piezoelectric actuator including a substrate, an insulating layer formed on the substrate, an adhesive layer formed on the insulating layer, a Pt lower electrode layer formed on the adhesive layer, and a PZT piezoelectric layer formed on the Pt lower electrode layer, the adhesive layer is made of TiO x having a composition x which is graded so that the composition x on the side of thio insulating layer is larger than the composition x on the side of the Pt lower electrode layer.
1. A piezoelectric actuator comprising:
a substrate;
an insulating layer formed on said substrate;
a TiO x adhesive layer formed on said insulating layer having a composition x of from 0 to 2;
a Pt lower electrode layer formed on said TiO x adhesive layer; and
a PZT piezoelectric layer formed on said Pt lower electrode layer,
said composition x being graded so that said composition x on the side of said insulating layer is larger than said composition x on the side of said Pt lower electrode layer.
2. The piezoelectric actuator as set forth in claim 1 , wherein said composition x is continuously graded.
3. The piezoelectric actuator as set forth in claim 1 , wherein a difference between a maximum value and a minimum value of said composition x within said TiO x adhesive layer is larger than 0.3.
4. The piezoelectric actuator as set forth in claim 1 , wherein said composition x on the side of said insulating layer is close to 2, and said composition x on the side of said Pt lower electrode layer is close to 0.
5. The piezoelectric actuator as set forth in claim 1 , wherein said composition x on the side of said insulating layer is from 1.4 to 2, and said composition x on the side of said Pt lower electrode layer is from 0 to 1.45.
6. A method for manufacturing a piezoelectric actuator comprising:
forming an insulating layer on a substrate;
forming a TiO x adhesive on said insulating layer by a sputtering process using oxygen gas in such a way that a flow rate of said oxygen gas is decreased from a start timing of said sputtering process to an end timing of said sputtering process; and
forming a Pt lower electrode layer is said TiO x adhesive layer; and
forming a PZT piezoelectric layer on said Pt lower electrode layer.
7. The method as set forth in claim 6 , wherein the flow rate of said oxygen gas in said TiO x adhesive layer forming is continuously decreased.
8. The method as set forth in claim 6 , further comprising:
heating said substrate, said insulating layer, said TiO x adhesive layer and said Pt lower electrode layer in an oxygen atmosphere before forming said PZT piezoelectric layer.