Piezoelectric Element with Indium Oxide Interface
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Solution Overview
Problem
Piezoelectric elements with indium-tin-oxide (ITO) as the oxide conductive layer exhibit reduced electrostatic capacity and piezoelectric characteristics, leading to decreased performance, while being cost-effective, and existing solutions using expensive metals like iridium oxide do not offer significant improvements in manufacturing cost or stability.
Innovation Solution
A piezoelectric element configuration with an upper electrode layer containing In, where the interface region between the piezoelectric film and the oxide conductive layer has a specific binding energy peak intensity ratio γ/α ≤ 0.25, achieved through sputtering and heating treatments, utilizing ITO or other In-based oxide conductive layers to maintain high piezoelectric characteristics and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ITO is used as the oxide conductive layer, then manufacturing cost is reduced, but electrostatic capacity and piezoelectric characteristics deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the oxide conductive layer by introducing In-Ga-Zn-O system instead of pure ITO, and controls the Ga content within 5-40 at%. This parameter optimization maintains low cost while improving electrostatic capacity and piezoelectric characteristics through enhanced oxygen compensation capability at the interface.
Solution Approach 2:
The patent creates a composite oxide conductive layer containing In, Ga, and Zn elements (In-Ga-Zn-O) rather than using single-element oxides. This composite structure combines the cost advantages of ITO with the superior oxygen compensation properties of Ga-containing oxides, achieving both cost reduction and performance maintenance.
2Reliability
If expensive metal oxides like IrO2 are used as the oxide conductive layer, then piezoelectric characteristics are maintained, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces expensive metal oxides (IrO2, RuO2, PtO2) with a cost-effective In-Ga-Zn-O oxide conductive layer. The inexpensive material achieves comparable or superior performance through optimized composition and interface characteristics, eliminating the need for costly rare earth metals.
Solution Approach 2:
The patent optimizes the chemical composition parameters of the oxide conductive layer by controlling Ga content (5-40 at%) and forming specific interface structures with the piezoelectric film. This parameter control enables the use of inexpensive materials to achieve the same functional performance as expensive metals.
3Reliability
If the oxide conductive layer is provided adjacent to the piezoelectric film, then oxygen pore deterioration is suppressed, but manufacturing complexity increases
Solution Approach 1:
The oxide conductive layer serves multiple functions simultaneously: it acts as the upper electrode, provides oxygen compensation to suppress oxygen pore formation, and forms a protective interface with the piezoelectric film. This multi-functionality eliminates the need for separate layers, reducing structural complexity while maintaining reliability.
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
The proposed configuration maintains high piezoelectric characteristics and stability, reducing manufacturing costs by using ITO or similar In-based layers, ensuring long-term performance without deteriorating the electrostatic capacity.
Implementation Method 1
a sputtering step of forming a film of the oxide conductive layer containing In on the piezoelectric film
Implementation Method 2
a heating treatment at 350°C or higher
Implementation Method 3
an intensity profile of binding energy, which is acquired by an X-ray photoelectron spectroscopy measurement
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
There are provided an inexpensive piezoelectric element and a manufacturing method for a piezoelectric element, in which a decrease in piezoelectric characteristics is suppressed. The piezoelectric element is a piezoelectric element including, on a substrate in the following order, a lower electrode layer, a piezoelectric film containing a perovskite-type oxide as a main component, and an upper electrode layer, in which at least a region of the upper electrode layer closest to a side of the piezoelectric film is composed of an oxide conductive layer containing In, and regarding an interface region between the piezoelectric film and the oxide conductive layer of the upper electrode layer, in an intensity profile of binding energy, which is acquired by an X-ray photoelectron spectroscopy measurement, in a case where a peak intensity of binding energy derived from a 3d5/2 orbital of In bonded to oxygen is denoted as α, and a peak intensity of binding energy derived from a 3d5/2 orbital of In bonded to an OH group is denoted as γ, a peak intensity ratio γ/α satisfies Expression (1). γ/α≤0.25