Graphene Oxide Bolometer Vertical Pillar Support Structure
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Solution Overview
Problem
Conventional IR bolometers face limitations in speed and spatial resolution due to high thermal time constants and the need for serpentine leg structures, which compromise pixel size and optical fill-factor, making it difficult to manufacture thermal imaging arrays with high spatial resolution.
Innovation Solution
The use of a bolometer structure comprising a substrate with SiGe and Si layers, a reduced graphene oxide absorber, and a partially reduced graphene oxide thermistor, supported by vertical pillars instead of serpentine legs, reduces thermal mass and heat capacity, allowing for faster response times and improved spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional serpentine leg structures are used to provide thermal isolation, then thermal conductance is reduced, but thermal mass and heat capacity increase, limiting speed and spatial resolution
Solution Approach 1:
The support structure is divided into multiple vertical pillars instead of continuous serpentine legs. This segmentation reduces the thermal mass while maintaining thermal isolation, as each pillar acts as an independent thermal barrier. The discontinuous structure minimizes heat capacity compared to continuous serpentine paths.
Solution Approach 2:
The support structure transitions from lateral serpentine legs to vertical pillars. This dimensional change from horizontal to vertical orientation reduces the thermal path length and minimizes the volume of material requiring thermal isolation, thereby reducing heat capacity while maintaining isolation effectiveness.
2Reliability
If serpentine leg structures are used for thermal isolation, then thermal conductance is reduced, but pixel area is sacrificed, reducing optical fill-factor
Solution Approach 1:
The support structure is segmented into discrete vertical pillars rather than continuous serpentine legs. This segmentation minimizes the lateral footprint required for thermal isolation, freeing up pixel area for optical collection while maintaining the necessary thermal barrier function.
Solution Approach 2:
Thermal isolation is achieved through vertical pillars extending in the z-dimension rather than lateral serpentine paths in the x-y plane. This dimensional reorientation preserves optical fill-factor by minimizing the lateral area occupied by support structures while maintaining effective thermal isolation.
3Ease of manufacture
If conventional bolometer structures with high thermal mass are used, then manufacturing is simplified, but speed and spatial resolution are limited
Solution Approach 1:
The support structure is segmented into vertical pillars that can be fabricated using standard semiconductor processing techniques such as deep reactive ion etching. This segmentation enables precise control of pillar dimensions and spacing, achieving high spatial resolution while remaining compatible with conventional manufacturing processes.
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 results in a five-fold reduction in heat capacity and a corresponding increase in speed, enabling higher spatial resolution and faster response times compared to conventional bolometers, while maintaining nearly 100% absorption of IR radiation.
Implementation Method 1
A photon 102 is absorbed by an absorber 104 having a low thermal mass. Absorber 104 is in thermal contact with film 106. Together absorber 104 and film 106 form a bolometer bridge assembly 107. The energy of photon 102 (Eph) absorbed by absorber 104 is converted into heat causing a slight increase in the temperature of assembly 107.
Implementation Method 2
Film 106 has much smaller thermal mass than absorber 104. Together absorber 104 and film 106 form a bolometer bridge assembly 107. Film 106 is constructed from a material whose electrical resistance varies with temperature in a known manner. Thus, the change in resistance of film 106 will correspond to the change in temperature of assembly 107.
Data Source
AI summary
Bolometers and methods of forming the same are provided. A bolometer that includes a substrate, a support structure comprising at least one SiGe layer and at least one Si layer, an absorber comprising reduced graphene oxide, and a thermistor comprising partially reduced graphene oxide are described. Also described are methods for forming bolometers and the parts contained therein.