Piezoelectric Thin Film Element with Oxide Buffer Layer
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Solution Overview
Problem
Piezoelectric thin film elements suffer from oxygen defects during film formation or when reacting with adjacent electrode layers, leading to inhibited piezoelectric properties and increased leakage current density.
Innovation Solution
Incorporating oxide particles such as NaNbO3, KNbO3, Nb2O5, or PtO2 into the electrode layers, with a content ratio of 5% to 20% by weight, to compensate for oxygen defects and optimize the crystal structure of the potassium-sodium niobate based piezoelectric thin films, ensuring even electrical field application and improved piezoelectric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sputtering or CVD method is used to form piezoelectric thin film, then productivity and downsizing are improved, but oxygen defects occur leading to deteriorated piezoelectric properties and increased leakage current density
Solution Approach 1:
A buffer layer comprising platinum oxide particles is introduced as an intermediary between the electrode layer and the piezoelectric thin film. This buffer layer serves as an oxygen source to compensate for oxygen defects that occur during sputtering or CVD film formation, thereby maintaining high piezoelectric properties while enabling productive thin film fabrication methods.
Solution Approach 2:
The buffer layer with platinum oxide particles is formed in advance before depositing the piezoelectric thin film. This preliminary action ensures that oxygen is available at the interface during subsequent film formation, preventing oxygen defects from occurring in the piezoelectric layer while maintaining productivity of the overall fabrication process.
2Ease of manufacture
If electrode layer reacts with piezoelectric thin film, then integration is improved, but oxygen defects are generated leading to increased leakage current density
Solution Approach 1:
The buffer layer of platinum oxide particles acts as an intermediary between the electrode layer and piezoelectric thin film. It allows for controlled interaction while releasing oxygen to compensate for defects, thus enabling good integration between layers while preventing harmful oxygen depletion that would increase leakage current.
Solution Approach 2:
The potential harmful reaction between the electrode layer and piezoelectric film is converted into a beneficial process. The buffer layer controls the interaction to release oxygen that compensates for oxygen defects, transforming what would be a harmful oxygen-depleting reaction into a beneficial oxygen-supplying process that improves piezoelectric properties.
3Reliability
If buffer layer with platinum oxide particles is introduced, then oxygen defects are compensated and piezoelectric properties are improved, but device structure becomes more complex
Solution Approach 1:
Rather than changing the entire device structure, the buffer layer is introduced only at the critical interface region between the electrode and piezoelectric film. This localized approach compensates for oxygen defects where they occur most frequently without adding complexity to the overall device structure.
Solution Approach 2:
The buffer layer is designed with specific parameters (platinum oxide particle size of 1-100 nm, concentration of 1-20 at%, thickness of 1-10 nm) that optimize its oxygen-release function while minimizing structural complexity. By controlling these parameters, the buffer layer effectively compensates for oxygen defects without significantly increasing device complexity.
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 solution effectively reduces leakage current density and enhances piezoelectric properties, allowing for higher displacement and improved performance in piezoelectric actuators and sensors, including applications in hard-disk drives and ink jet printers.
Implementation Method 1
the piezoelectric sensors, e.g., gyro sensors, pressure sensors, pulse sensors, shock sensors and microphones, have been developed by using the piezoelectric effect that converses the force applied to the piezoelectric thin film into a voltage
Implementation Method 2
piezoelectric actuators, e.g., the head assembly in a hard-disk drive and the head in an ink jet printer, have been developed by using the inverse piezoelectric effect which makes the piezoelectric thin film deformed when a voltage is applied to the piezoelectric thin film
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A piezoelectric element is proposed comprising a piezoelectric thin film (3), preferably of potassium sodium niobate, sandwiched between a pair of electrode layers (2, 4) composed of platinum (Pt). Oxide particles are contained in at least one of the electrode layers, the particles being oxides of Pt or at least one element constituting the piezoelectric thin film, preferably PtO2, NaNbO3, KNbO3, or Nb2O5.