LiNbO3 Surface Acoustic Wave Stack for Wider Euler Angle Coupling
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Solution Overview
Problem
Current surface acoustic wave devices using LiNbO3 thin films on sapphire substrates have limited Euler angles for increased electromechanical coupling, and those using diamond substrates are costly due to diamond's high expense.
Innovation Solution
A surface acoustic wave device with a LiNbO3 single-crystal plate on a high acoustic-velocity substrate, such as silicon carbide or alumina, with Euler angles ranging from 0° to 160° and -5° to +5°, and a thickness of 0.05λ to 1.6λ, to enhance acoustic velocity and electromechanical coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a LiNbO3 thin film is formed on a (012) sapphire substrate, then the electromechanical coupling coefficient can be increased, but the range of Euler angles where the electromechanical coupling coefficient can be increased is limited to a narrow range
Solution Approach 1:
The patent changes the substrate material parameter from sapphire to high acoustic-velocity substrates (such as diamond, SiC, or alumina) with specific acoustic velocity ranges (5400-8660 m/sec or higher). This parameter change enables the LiNbO3 layer to achieve increased electromechanical coupling coefficient across a broader range of Euler angles (0° to 160° and -5° to +5°), resolving the contradiction between coupling coefficient improvement and angular range limitation.
2Reliability
If a LiNbO3 single-crystal layer is stacked on a diamond substrate, then the acoustic velocity of the surface acoustic wave and the electromechanical coupling coefficient can be increased, but the cost increases due to the expensive diamond substrate
Solution Approach 1:
The patent replaces the expensive diamond substrate with cheaper alternative substrates that have high acoustic velocity properties, such as SiC (silicon carbide), alumina (aluminum oxide), or other substrates with acoustic velocity of 5400-8660 m/sec or higher. These alternative substrates can achieve similar acoustic velocity and electromechanical coupling coefficient improvements without the high cost of diamond, thus resolving the contradiction between performance improvement and manufacturing cost.
3Reliability
If the thickness of the LiNbO3 single-crystal plate is increased, then the electromechanical coupling coefficient can be increased, but the acoustic velocity may be affected
Solution Approach 1:
The patent optimizes the thickness parameter of the LiNbO3 single-crystal plate to be within the range of 0.05λ to 1.6λ (where λ is the wavelength of the surface acoustic wave). This thickness optimization, combined with the use of high acoustic-velocity substrates, enables simultaneous achievement of increased electromechanical coupling coefficient and maintained acoustic velocity, resolving the contradiction between coupling coefficient improvement and acoustic velocity preservation.
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 configuration increases acoustic velocity and electromechanical coupling coefficients while reducing costs by using less expensive high-acoustic-velocity substrates, offering a wider range of Euler angles for improved performance.
Implementation Method 1
a surface acoustic wave device comprising a piezoelectric substrate including a high acoustic-velocity substrate in which an acoustic velocity of a transverse wave is 5400 m/sec or higher and 8660 m/sec or lower, and a LiNbO3 single-crystal plate formed on the high acoustic-velocity substrate
Implementation Method 2
in which an acoustic velocity of a transverse wave is 5400 m/sec or higher and 8660 m/sec or lower... the acoustic velocity of a surface acoustic wave can be raised
Data Source
Figure 1(a)~1(c)
Figure 2~3
Figure 4~5
AI summary
A surface acoustic wave device is provided which can increase the acoustic velocity of a surface acoustic wave the electromechanical coupling coefficient k2, and which is inexpensive. A surface acoustic wave device (1) includes a piezoelectric substrate in which a LiNbO3 single-crystal plate (3) having Euler angles (0°, 67° to 160°, -5° to +5°) or (90°, 51° to 133°, -5° to +5°) is formed on a high acoustic-velocity substrate (2) in which an acoustic velocity of a transverse wave is 5400 m/sec or higher and 8660 m/sec or lower, and an electrode (4) formed on the piezoelectric substrate and made of metal.