Ferroelectric Sensor Polarization Control for Sensitivity
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Solution Overview
Problem
Thermal-type infrared sensors, such as pyroelectric sensors, face challenges in achieving high sensitivity when using thin films due to difficulties in producing sensors from bulk materials, leading to reduced performance.
Innovation Solution
A sensor configuration that includes a ferroelectric element with a ferroelectric film between two electrodes, where specific voltage applications align and reverse polarization directions to detect temperature changes based on coercive voltage variations, improving sensitivity and reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of one pixel of pyroelectric material is made very small to improve sensitivity and responsivity, then sensitivity and responsivity are improved, but it becomes difficult to produce a sensor from bulk material
Solution Approach 1:
The patent uses a thin film pyroelectric layer formed by spin-coating technique instead of bulk material. This allows the pyroelectric material to be deposited as a thin flexible film on a substrate, enabling miniaturization to pixel sizes while maintaining manufacturability through solution-based processing rather than bulk material fabrication
Solution Approach 2:
The patent changes the physical state and form of the pyroelectric material from bulk to thin film, and further optimizes by controlling the thickness parameter of the thin film. This parameter change enables both small pixel sizes for high sensitivity and compatibility with solution-based fabrication methods for ease of manufacture
2Ease of manufacture
If spin-coated PZT thin film is used to enable production, then manufacturability is improved, but infrared sensor sensitivity becomes poor
Solution Approach 1:
The patent uses a composite structure consisting of a spin-coated PZT thin film pyroelectric layer combined with specific electrode configurations and optical microlens structures. This composite approach maintains the manufacturability advantage of spin-coating while compensating for sensitivity losses through optimized multi-layer design
Solution Approach 2:
The patent optimizes the local properties of the thin film structure by controlling the thickness and composition of the PZT layer in specific regions, and by adding optical microlenses at specific locations to enhance light absorption and heat generation locally, thereby improving sensitivity without sacrificing the overall manufacturability of the thin film approach
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 proposed solution significantly enhances sensor sensitivity by leveraging the variation in coercive voltage with temperature, achieving improved reproducibility and reliability in temperature detection, particularly with materials like PZT or lead-free complex oxides.
Implementation Method 1
a ferroelectric element that is disposed between the first electrode and the second electrode and that has a ferroelectric film formed of a ferroelectric substance
Implementation Method 2
A pyroelectric element has the property of absorbing thermal energy of infrared rays to cause a temperature change and inducing electric charges in accordance with the temperature change
Implementation Method 3
Temperature can be detected using the amount of reversed polarization based on a variation in the coercive voltage caused by a change of the temperature
Implementation Method 4
A pyroelectric element has the property of absorbing thermal energy of infrared rays to cause a temperature change
Data Source
AI summary
A sensor includes a first electrode, a second electrode, a ferroelectric element that is disposed between the first electrode and the second electrode and that has a ferroelectric film formed of a ferroelectric substance, and a detector configured to read an electric charge generated in the ferroelectric element. The detector performs reading by applying a first voltage for aligning polarization directions of the ferroelectric film and a second voltage for reversing polarization of at least part of the ferroelectric film whose polarization directions have been aligned.