Diamond Piezoresistor Sensitivity via Crystal Orientation
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Solution Overview
Problem
Existing force detection devices using diamond piezoresistors lack effective utilization of crystal orientation dependency, leading to reduced piezoresistance coefficients and limited sensitivity, especially at high temperatures and under varying stress conditions.
Innovation Solution
A force detection device utilizing a highly orientated diamond piezoresistor with boron as an impurity, where the diamond piezoresistor is formed on specific crystal planes and subjected to stress aligned with or perpendicular to the input electrodes, leveraging crystal orientation dependency to enhance piezoresistance coefficients and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diamond piezoresistor is used without considering crystal orientation, then the device can be manufactured with simpler processes, but the piezoresistance coefficient is reduced and sensitivity is limited
Solution Approach 1:
The patent changes the crystal orientation parameter of the diamond piezoresistor from random or conventional orientations to highly oriented configurations, specifically aligning the <100> crystal direction with the stress direction. This parameter change maximizes the piezoresistance coefficient and enhances sensitivity without fundamentally altering the manufacturing process complexity
Solution Approach 2:
The patent introduces asymmetry in the crystal orientation arrangement, where the diamond piezoresistor is deliberately oriented with its <100> direction aligned with the stress direction rather than using symmetric or random orientations. This asymmetric orientation configuration optimizes the piezoresistive effect and improves measurement sensitivity
2Reliability
If conventional diamond piezoresistors are used at high temperatures, then the device can operate in elevated temperature environments, but the piezoresistance coefficient decreases and stability is reduced
Solution Approach 1:
The patent changes the crystal orientation parameter to highly oriented configurations with <100> alignment, which maintains higher piezoresistance coefficients at elevated temperatures compared to conventional orientations. This parameter change enables reliable operation at high temperatures while preserving sensitivity
Solution Approach 2:
The patent uses boron-doped diamond material that, while having finite temperature stability limits, provides sufficient operational lifetime at elevated temperatures for the intended application. The material is selected to balance cost, manufacturability, and temperature stability requirements
3Measurement precision
If the diamond piezoresistor is oriented without specific crystal plane alignment, then the manufacturing process is simpler, but the piezoresistance coefficient is not maximized
Solution Approach 1:
The patent specifies the crystal plane orientation parameter, using <100> oriented diamond surfaces for the piezoresistor configuration. This parameter specification maximizes the piezoresistance coefficient while maintaining compatibility with existing diamond growth and processing technologies
Solution Approach 2:
The patent performs preliminary crystal orientation selection during the diamond substrate preparation stage, ensuring that <100> oriented surfaces are used before piezoresistor fabrication begins. This preliminary action simplifies subsequent manufacturing steps and ensures optimal piezoresistive properties without requiring complex real-time orientation control during fabrication
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 device achieves increased sensitivity and stability under high-temperature conditions by maximizing piezoresistance coefficients, allowing for effective detection of various types of stress, including in-plane and out-of-plane stresses, through strategic orientation and alignment of the diamond piezoresistor.
Implementation Method 1
a force detection device is provided with a piezoresistor including diamond into which boron is introduced as an impurity. The force detection device utilizes the crystal orientation dependency of the piezoresistor.
Implementation Method 2
the piezoresistive effect of a piezoresistor formed on the (100) plane of a substrate in the [100] direction is described
Data Source
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AI summary
A force detection device includes a diamond piezoresistor including a highly orientated diamond into which boron is introduced as an impurity. The absolute value of the piezoresistance coefficient of the diamond piezoresistor is greater than the absolute value of a piezoresistance coefficient π11 or π12 in a case in which a major axis is in the <100> direction.