Infrared Sensor Beam with Phononic Crystal Structure
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Solution Overview
Problem
Current thermal infrared sensors face limitations in enhancing sensitivity due to insufficient heat insulation performance, which affects their ability to detect infrared light effectively.
Innovation Solution
The infrared sensor design incorporates a beam with a p-type and n-type semiconductor portion, featuring a three-dimensional phononic crystal structure with recesses and solid portions, where the smallest dimension of these portions is less than or equal to 100 nanometers, reducing thermal conductivity and increasing heat-insulating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a beam with phononic crystal structure is used to thermally insulate the infrared light receiver from the base substrate, then the sensitivity to infrared light is improved, but the thermal conductivity reduction is insufficient to achieve higher sensitivity
Solution Approach 1:
The beam is divided into multiple sections with alternating p-type and n-type semiconductor portions. Each section contains recesses that segment the solid material into isolated solid portions with smallest dimensions of 100 nm or less. This segmentation creates phonon scattering interfaces that significantly reduce thermal conductivity while maintaining structural integrity for mechanical support.
Solution Approach 2:
Different portions of the beam are assigned different semiconductor types (p-type and n-type) with distinct thermal and electrical properties. The recesses are strategically positioned to create local variations in thermal conductivity, with solid portions between recesses having minimized dimensions to enhance phonon scattering. This local differentiation optimizes both thermal insulation and electrical functionality in specific regions.
2Loss of energy
If the solid portion dimension is reduced to less than or equal to 100 nanometers to reduce thermal conductivity, then heat insulation performance is improved, but the mechanical strength may be compromised
Solution Approach 1:
The beam is constructed as a composite structure alternating between p-type and n-type semiconductor materials. This composite architecture provides mechanical reinforcement through the combination of different material properties, compensating for the reduced cross-sectional area of solid portions. The alternating structure creates a mechanically robust beam that maintains sufficient strength despite the nanoscale dimensions of solid portions required for optimal thermal insulation.
Solution Approach 2:
The beam structure segments the material into periodically arranged solid portions separated by recesses. This segmentation creates a hierarchical structure where the periodic arrangement provides mechanical stability while the nanoscale solid portion dimensions (≤100 nm) maximize phonon scattering. The segmented design allows the beam to maintain structural integrity through distributed load bearing across multiple solid portions rather than relying on any single continuous material path.
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 design enhances the sensitivity of the infrared sensor by improving heat-insulating properties, allowing for better detection of infrared light through reduced thermal conductivity and increased mechanical strength.
Implementation Method 1
the phononic crystal structure of this type is a periodic structure in which the smallest unit that constitutes the arrangement of the through holes is a unit lattice. The thermal conductivity of a thin film can be reduced by, for example, forming the thin film to be porous. This is because the thermal conductivity of the thin film is decreased by gaps that are introduced in the thin film as a result of the thin film being formed to be porous.
Data Source
AI summary
An infrared sensor includes a base substrate, an infrared light receiver, and a beam. The beam includes a separated portion separated from the base substrate to be suspended above the base substrate. The beam is connected at the separated portion to the infrared light receiver. The beam includes a p-type portion containing a p-type semiconductor and an n-type portion containing an n-type semiconductor. The p-type portion has a first three-dimensional structure including first recesses and a first solid portion formed between the first recesses. The first solid portion has, between the first recesses adjacent to each other in plan view, a smallest dimension of less than or equal to 100 nanometers in plan view. The n-type portion has a second three-dimensional structure including second recesses and a second solid portion formed between the second recesses. The second solid portion has, between the second recesses adjacent to each other in plan view, a smallest dimension of less than or equal to 100 nanometers in plan view. The beam satisfies at least one of following conditions (Ia) or (IIa): (Ia) the first solid portion includes a first portion having a Young's modulus of less than or equal to 80% of a Young's modulus of a first reference sample that is made of a material of a type identical to a type of a material constituting the first solid portion and that does not have recesses; and (IIa) the second solid portion includes a second portion having a Young's modulus of less than or equal to 80% of a Young's modulus of a second reference sample that is made of a material of a type identical to a type of a material constituting the second solid portion and that does not have recesses.