PIEZOELECTRIC FILM LAMINATE AND DEVICE INCLUDING PIEZOELECTRIC FILM LAMINATE

Abstract

A piezoelectric film laminate includes a lithium tantalate substrate, and a lead zirconate titanate niobate layer formed above the lithium tantalate substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a piezoelectric film laminate in accordance with a first embodiment of the invention.

FIG. 2 is a view schematically showing a lithium tantalate crystal in hexagonal.

FIG. 3 is a view schematically showing a tilt of a lead zirconate titanate niobate layer with respect to a lithium tantalate substrate.

FIG. 4 is a view schematically showing the relation between the cut angle of a Y-cut lithium tantalate substrate and a (012) plane.

FIG. 5 is a 2 θ-θ scanning X-ray diffraction diagram of a KNbO₃ layer in accordance with a first experimental example.

FIG. 6 is a φ scanning X-ray diffraction diagram of the KNbO₃ layer in accordance with the first experimental example.

FIG. 7 is a view showing the orientation relation of a cubic PZTN layer with respect to a LiTaO₃ substrate, in accordance with the first experimental example.

FIGS. 8A and 8B are views showing the orientation relation of a rhombohedral PZTN layer with respect to a LiTaO₃ substrate, in accordance with a second experimental example.

FIGS. 9A and 9B are views showing the orientation relation of a tetragonal PZTN layer with respect to a LiTaO₃ substrate, in accordance with a third experimental example.

FIG. 10 is a cross-sectional view of a surface acoustic wave device in accordance with a second embodiment of the invention.

FIG. 11 is a perspective view of a frequency filter in accordance with the second embodiment of the invention.

FIG. 12 is a perspective view of an oscillator in accordance with the second embodiment of the invention.

FIG. 13 is a schematic view of an example in which the oscillator in accordance with the second embodiment is applied to a VCSO.

FIG. 14 is a schematic view of an example in which the oscillator in accordance with the second embodiment is applied to a VCSO.

FIG. 15 is a block diagram of the basic structure of a PLL circuit.

FIG. 16 is a block diagram showing the structure of an electronic circuit in accordance with the second embodiment of the invention.

FIG. 17 is a view showing a communications system that uses a reader/writer in accordance with the second embodiment of the invention.

FIG. 18 is a schematic block diagram of the communications system shown in FIG. 17.

Claims

1. A piezoelectric film laminate comprising: a lithium tantalate substrate; anda lead zirconate titanate niobate layer formed above the lithium tantalate substrate.

2. A piezoelectric film laminate according to claim 1, wherein the lithium tantalate substrate is a 36°-42° Y-cut signal crystal substrate.

3. A piezoelectric film laminate according to claim 2, wherein the lead zirconate titanate niobate layer is oriented in a (100) plane in a cubic system expression, and an angle defined between the (100) plane and a surface of the lithium tantalate substrate is 3° or greater but 10° or smaller.

4. A piezoelectric film laminate according to claim 3, wherein a cubic (100) plane of the lead zirconate titanate niobate layer is in parallel with a (012) plane of the lithium tantalate substrate.

5. A piezoelectric film laminate according to claim 4, wherein a [011] vector of the lead zirconate titanate niobate layer is epitaxially grown in a direction in parallel with a [−2110] vector of the lithium tantalate substrate.

6. A piezoelectric film laminate according to claim 5, wherein the lead zirconate titanate niobate layer is in a rhombohedral (100) orientation, and a vector formed by projecting a polarization vector [111] thereof to a (012) plane of the lithium tantalate substrate is in parallel and in the same orientation with a vector formed by projecting a polarization vector of the lithium tantalate substrate to the (012) plane.

7. A piezoelectric film laminate according to claim 5, wherein the lead zirconate titanate niobate layer is in a tetragonal (001) orientation, and a polarization vector [001] thereof is in parallel and in the same orientation with a vector formed by projecting a polarization vector of the lithium tantalate substrate to a normal vector of the (012) plane of the lithium tantalate.

8. A device comprising the piezoelectric film laminate set forth in claim 1.