ScAlN Sapphire SAW Sensor Sezawa Wave Sensitivity
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Solution Overview
Problem
Surface acoustic wave (SAW) sensors with ScAlN/SiC structures experience reduced detection sensitivity due to the acoustoelastic effect, which affects the change in frequency, delay time, and phase of the SAW element when distorted by physical quantities, leading to lower sensing accuracy.
Innovation Solution
A SAW sensor with a ScAlN/sapphire structure is used, where the ScAlN film is formed on a sapphire board, reducing the acoustoelastic effect and enhancing detection sensitivity by employing a comb-teeth electrode to excite surface acoustic waves, specifically utilizing Sezawa waves to distribute energy deeper into the substrate, thereby minimizing the acoustoelastic effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ScAlN/SiC structure is used, then heat resistance is improved, but detection sensitivity deteriorates due to acoustoelastic effect
Solution Approach 1:
The patent changes the substrate material parameter from SiC to sapphire while maintaining the ScAlN piezoelectric film, thereby altering the acoustoelastic characteristics of the SAW material to reduce the harmful acoustoelastic effect and improve detection sensitivity
Solution Approach 2:
The patent uses a composite structure of ScAlN film on sapphire substrate, combining the high piezoelectricity of ScAlN with the low acoustoelastic effect of sapphire to achieve both high sensitivity and high temperature resistance
2Power
If ScAlN/SiC structure is used, then piezoelectric performance is improved, but sensing accuracy deteriorates due to acoustoelastic effect
Solution Approach 1:
The patent changes the substrate material parameter from SiC to sapphire, which has different elastic properties that reduce the acoustoelastic effect, thereby improving sensing accuracy while maintaining the high piezoelectric performance of the ScAlN film
3Measurement precision
If SAW material is distorted by physical quantity, then physical quantity detection is enabled, but frequency change is reduced due to acoustoelastic effect
Solution Approach 1:
The patent changes the material composition parameter by replacing SiC substrate with sapphire substrate, which has lower acoustoelastic coefficients, thereby enabling larger frequency changes when the SAW material is distorted by physical quantities and improving detection sensitivity
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 ScAlN/sapphire structure significantly improves detection sensitivity by reducing the acoustoelastic effect, resulting in higher sensitivity for physical quantity detection compared to SAW sensors with ScAlN/SiC structures, as demonstrated by the smaller acoustoelastic coefficients and experimental results showing increased phase change relative to load.
Implementation Method 1
The ScAlN film is a piezoelectric thin film
Implementation Method 2
the comb-teeth electrode is arranged on the surface acoustic wave material to excite surface acoustic wave to the surface acoustic wave material
Data Source
AI summary
A surface acoustic wave (SAW) sensor includes a surface acoustic wave material and a comb-teeth electrode. The surface acoustic wave material is to be arranged at a place where the surface acoustic wave material is distorted by physical quantity such as stress. The comb-teeth electrode is arranged on the surface of the surface acoustic wave material to excite a surface acoustic wave to the surface acoustic wave material. The surface acoustic wave material has a sapphire board and a ScAlN film arranged on a surface of the sapphire board.