Transparent Piezoelectric Layer Doping to Balance Cracking and Output
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Solution Overview
Problem
Piezoelectric devices face challenges in achieving satisfactory optical and piezoelectric characteristics due to the trade-off between thickness, where a thicker layer improves crystal orientation but increases cracking, and a thinner layer compromises piezoelectric performance.
Innovation Solution
A piezoelectric device with a wurtzite crystal material layer, incorporating a predetermined amount of impurities like Mg or Si, is fabricated with a thin thickness range (50 nm to 400 nm) to enhance both optical and piezoelectric characteristics, using a stack configuration with an amorphous orientation control layer to prevent cracking and improve crystal alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric layer is made thicker to improve crystal orientation, then piezoelectric characteristics are improved, but cracking occurs more frequently
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the piezoelectric layer within 50-400 nm and adjusting the impurity concentration (0.01-5 atom%) to optimize both piezoelectric characteristics and crack resistance. This quantitative parameter optimization resolves the contradiction between thickness for piezoelectric performance and thinness for crack prevention
Solution Approach 2:
The patent uses composite materials by introducing impurity elements (Mg, Ca, Si, Al) into the ZnO piezoelectric layer to form a doped composite structure. This composite approach enhances crystal orientation and piezoelectric properties while maintaining layer integrity and reducing cracking tendencies
2Illumination intensity
If the piezoelectric layer is made thinner to reduce device dimensions, then optical characteristics are improved, but piezoelectric characteristics deteriorate
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the thickness to 50-400 nm (thin enough for optical transparency but thick enough for piezoelectric performance) and simultaneously adjusting impurity concentration to enhance crystal orientation. This dual parameter optimization ensures both optical transmittance and piezoelectric characteristics are satisfied
Solution Approach 2:
The patent employs composite materials by doping the thin piezoelectric layer with impurity elements that enhance crystal orientation and piezoelectric properties. This composite structure compensates for the reduced piezoelectric performance that would normally result from thinning the layer, while maintaining excellent optical characteristics
3Reliability
If impurity concentration is increased to improve piezoelectric characteristics, then piezoelectric performance is enhanced, but optical transparency may be compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the impurity concentration within 0.01-5 atom%, which is sufficient to enhance crystal orientation and piezoelectric characteristics while remaining low enough to preserve optical transparency. This optimized concentration range resolves the contradiction between piezoelectric enhancement and optical clarity
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 achieves improved optical transparency and piezoelectric performance, with transmittance of 50% or more at 380 nm and haze of 3% or less, while minimizing cracking and leakage current issues.
Implementation Method 1
Piezoelectric devices, which make use of the piezoelectric effect of substances, have conventionally been adopted. The piezoelectric effect is a phenomenon in which microscopic polarization is produced in response to a mechanical stress applied to a substance.
Implementation Method 2
Another conventional technique is to apply a paste of a mixture of MgO and varnish onto an oriented ZnO film formed by a vapor transport method, and to diffuse Mg into the oriented ZnO film by thermal diffusion.
Implementation Method 3
A sintered film of a piezoelectric material is known, where a chemical solution that contains a compound having a wurtzite crystal structure to which an alkaline earth metal, such as magnesium (Mg), calcium (Ca) or the like is added, is applied by a sol-gel process and sintered.
Data Source
AI summary
For a piezoelectric device, an optical characteristic and/or a piezoelectric characteristic is improved. A piezoelectric device has a first electrode layer, a second electrode layer, and a piezoelectric layer provided between the first electrode layer and the second electrode layer, wherein the piezoelectric layer is formed of a wurtzite crystal material as a main component, to which one or more elements is/are added, said one or more elements being transparent when turned into an oxide, and wherein a haze value is 3% or less, and transmittance with respect to light having a wavelength of 380 nm is 50% or more.