Thin Film Piezoelectric Element With Roughened Electrode Interface

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Solution Overview

Problem

The challenge is to increase the displacement of thin-film piezoelectric elements while maintaining their planar shape and layer structure, as the existing methods for improving piezoelectric properties are limited by the size and structure of the elements, and surface roughness optimization is crucial for enhancing contact area and crystallinity.

Innovation Solution

A thin-film piezoelectric element with a pair of electrode layers and a piezoelectric thin film, where the surface roughness of the interface between the piezoelectric thin film and the electrode layers is between 220 nm and 500 nm, achieved through mechanical or chemical treatment, resulting in a larger real contact area and improved crystallinity, thereby increasing displacement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the size of the planar shape or the layer structure of a thin-film piezoelectric element is limited, then the element can be miniaturized and mass productivity is improved, but the amount of displacement of the thin-film piezoelectric element is limited

Engineering Contradiction:

Improvesize of thin-film piezoelectric elementVSAvoidamount of displacement

Core Design Contradiction:

Volume of moving objectVSLength of moving object

Solution Approach 1:

The patent introduces surface roughness as a new dimensional parameter to increase the real contact area between the piezoelectric thin film and electrode layer. By creating micro-scale protrusions and recesses on the electrode layer surface, the contact area is expanded from a two-dimensional plane to a three-dimensional textured surface, thereby increasing displacement without enlarging the overall element footprint.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The electrode layer is designed with a porous or textured surface structure containing numerous micro-protrusions and recesses. This porous-like morphology increases the effective contact area with the piezoelectric thin film, allowing greater displacement output from the same planar footprint.

Inventive Principle:

Principle #31Porous materials

2Manufacturing precision

If the surface roughness of the electrode layer is reduced to improve crystal orientation, then piezoelectric properties are improved, but the contact area between the piezoelectric thin film and electrode layer is reduced

Engineering Contradiction:

Improvecrystal orientationVSAvoidcontact area

Core Design Contradiction:

Manufacturing precisionVSArea of stationary object

Solution Approach 1:

The patent applies local quality by creating specific micro-scale protrusions and recesses in certain regions of the electrode layer surface. This localized texturing provides both sufficient contact area in the rough regions and maintains smooth regions for proper crystal orientation, achieving both goals simultaneously through spatial differentiation of surface properties.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent resolves this contradiction by transitioning from a flat two-dimensional surface to a three-dimensional textured surface with controlled roughness. The micro-protrusions and recesses increase the real contact area while the overall surface topology is optimized to maintain proper crystal orientation during piezoelectric thin film formation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach allows for a significant increase in the displacement of thin-film piezoelectric elements, enhancing the performance of both sensors and actuators, including those used in hard disk drives and ink jet printers, by maintaining satisfactory crystallinity and contact area.

Implementation Method 1

head assemblies for hard disk drives and ink jet print heads, which serve as piezoelectric actuators using an inverse piezoelectric effect, in which a piezoelectric thin film is deformed by the application of a voltage to the piezoelectric thin film

Methodology Applied

Scientific EffectInverse piezoelectric effect: Piezoelectric Effect

Implementation Method 2

gyroscope sensors, pressure sensors, pulse wave sensors, shock sensors, and microphones, which serve as piezoelectric sensors using a piezoelectric effect, in which a force applied to a piezoelectric thin film is converted into a voltage

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS9147826B2Thin film piezoelectric element, thin film piezoelectric actuator, and thin film piezoelectric sensor; and hard disk drive, and inkjet printer

Publication Date: 2015.09.29 TDK CORP

AI summary

An object is to increase the amount of displacement of a thin-film piezoelectric element including a piezoelectric thin film having an uneven-shaped contact surface with the planar shape and the layer structure of the thin-film piezoelectric element kept unchanged. The thin-film piezoelectric element includes a pair of electrode layers and a piezoelectric thin film sandwiched between the pair of electrode layers, in which a surface roughness P-V of an interface between the piezoelectric thin film and at least one of the pair of electrode layers is 220 nm or more and 500 nm or less.