Piezoelectric thin film element

Abstract

A piezoelectric thin film element includes a bottom electrode, a piezoelectric layer, and a top electrode on a substrate. The piezoelectric layer includes, as a main phase, a perovskite-type oxide. The bottom electrode has a surface roughness of not more than 0.86 nm in arithmetic mean roughness Ra or not more than 1.1 nm in root mean square roughness Rms. The bottom electrode has a (111) preferential orientation in a direction perpendicular to the substrate.

1 . A piezoelectric thin film element, comprising:
 a bottom electrode;   a piezoelectric layer; and   a top electrode on a substrate,   wherein the piezoelectric layer comprises, as a main phase, a perovskite-type oxide,   wherein the bottom electrode has a surface roughness of not more than 0.86 nm in arithmetic mean roughness Ra or not more than 1.1 nm in root mean square roughness Rms, and   wherein the bottom electrode has a (111) preferential orientation in a direction perpendicular to the substrate.   
     
     
         2 . The piezoelectric thin film element according to  claim 1 , wherein the piezoelectric layer formed on the bottom electrode has a maximum-minimum surface roughness of not more than 23% with respect to an average film thickness of the piezoelectric layer. 
     
     
         3 . The piezoelectric thin film element according to  claim 1 , wherein the piezoelectric layer formed on the bottom electrode has the arithmetic mean surface roughness Ra or the root mean square surface roughness Rms of not more than 2.7% with respect to an average film thickness of the piezoelectric layer. 
     
     
         4 . The piezoelectric thin film element according to  claim 1 , wherein the piezoelectric layer has the surface roughness of not more than 4.1 nm in arithmetic mean roughness Ra, not more than 4.8 nm in the root mean square roughness Rms, or not more than 137.7 nm in a maximum-minimum roughness. 
     
     
         5 . The piezoelectric thin film element according to  claim 1 , wherein the bottom electrode has the surface roughness of not more than 1.1 nm in the root mean square roughness Rms. 
     
     
         6 . A piezoelectric actuator, comprising:
 a piezoelectric thin film element according to  claim 1 ; and   a voltage application unit which applies a voltage to the piezoelectric thin film element.   
     
     
         7 . A piezoelectric sensor, comprising:
 a piezoelectric thin film element according to  claim 1 ; and   a voltage detecting unit which detects a voltage generated at the piezoelectric thin film element.