PIEZOELECTRIC DEVICE AND METHOD FOR MANUFACTURING PIEZOELECTRIC DEVICE
FIG1 is a schematic diagram of a piezoelectric sensor according to an embodiment  FIG2 shows cross-sectional transmission electron microscopy(TEM) images of stacking a piezoelectric layer over an orientation control layer of amorphous phase fabricated according to the embodiment
FIG1 is a schematic diagram of a piezoelectric sensor 10A which is an example of the piezoelectric device. The piezoelectric sensor 10A is formed in a layered structure including a pair of electrodes 11 and 19 and a plastic layer 12, in which a stacking 15 of an orientation control layer 13 and a piezoelectric layer 14 is provided between the electrodes 11 and 19. In the example of FIG1, the electrode 11 serves as a transparent bottom electrode, and the electrode 19 serves as a transparent top electrode. The transparency of the electrode 11 and the electrode 19 is not always required; however, when applied to a display, including a touch panel, it is desirable for the piezoelectric sensor 10A to have a transparent electrode made of ITO, IZO or the like. Although in the configuration of FIG1, the plastic layer 12 is provided between the electrode 11 and the stacking 15, the position of the plastic layer 12 is not limited to this example, and a suitable position may be selected as long as the plastic layer 12 imparts the flexibility to the piezoelectric sensor 10A.  FIG2 shows cross-sectional TEM images of the stacking of the orientation control layer 13 and the piezoelectric layer 14 actually fabricated over a plastic (PET) base film 20. FIG2 (A) is an enlarged view at magnifications of 500,000 times, and FIG2 (B) is an enlarged view at magnifications of 2 million times. Amorphous SAZO is used as the orientation control layer 13 and zinc oxide (ZnO) is used as the piezoelectric layer 14. In general, "AZO" comprised of ZnO as the basic component with Al2O3 added as a sub component is a conductive film with high crystallinity. By further adding SiO2, an amorphous and electrically insulating SAZO film can be obtained. The thickness of this orientation control layer 13 is 10 nm, and the thickness of the piezoelectric layer 14 is 50 nm. As can be observed from the TEM image of FIG2 (A), the piezoelectric layer 14 is formed over the amorphous orientation control layer 13 having a smooth and uniform surface. In the TEM image of FIG2 (B), a large number of lines running in the vertical direction of the piezoelectric layer 14 indicate the direction of crystal growth. It is clearly shown that the c-axis of the piezoelectric layer 14 is aligned vertical to the substrate.
cross-sectional view, schematic diagram
15
stacking
50
preferably is
10
piezoelectric device Example Examples
['1. A piezoelectric device comprising: a layered structure in which at least a first electrode, a plastic layer, an orientation control layer, a piezoelectric layer, and a second electrode are stacked, wherein the orientation control layer is amorphous, and the piezoelectric layer with a thickness of 20 nm to 250 nm is provided over the orientation control layer, the piezoelectric layer having a wurtzite crystal structure, and wherein the orientation control layer and the piezoelectric layer are provided between the first electrode and the second electrode.', '15. A manufacturing method of a piezoelectric device having a layered structure in which at least a first electrode, a plastic layer, an orientation control layer, a piezoelectric layer, and a second electrode are stacked, the method comprising: forming an orientation control layer in amorphous phase on the plastic layer or on a stacking of layers including the plastic layer, and forming the piezoelectric layer having a wurtzite crystal structure over the orientation control layer of the amorphous phase.']