Carbon Nanotube Bolometer Electrodes for Low-Resistance TCR Sensing
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Solution Overview
Problem
Existing bolometers using carbon nanotubes face challenges in achieving low resistance and high temperature coefficient resistance (TCR) due to the nature of the electrodes used, particularly when carbon nanotubes are jointed to gold electrodes, leading to high resistance values despite symmetrical linear IV characteristics.
Innovation Solution
The use of electrodes with a work function that is either lower than p-type semiconducting carbon nanotubes for Schottky junction formation or higher than n-type semiconducting carbon nanotubes, combined with a bolometer film comprising at least 90% semiconducting carbon nanotubes, to create asymmetrical IV characteristics and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gold electrodes are used to joint carbon nanotubes in a bolometer, then symmetrical linear IV characteristics are achieved, but high resistance values occur
Solution Approach 1:
The patent changes the work function parameter of the electrode material from gold (high work function) to metals with lower work function (such as aluminum, magnesium, calcium, or their alloys). This parameter change transforms the electrode-carbon nanotube junction from ohmic contact to Schottky contact, fundamentally altering the electrical characteristics to achieve both asymmetrical IV characteristics and low resistance values simultaneously
Solution Approach 2:
The patent employs composite electrode structures combining metals with different work functions. Specifically, it uses a multi-layer configuration where a low work function metal (Al, Mg, or Ca) forms the contact layer with carbon nanotubes, optionally combined with other metal layers. This composite structure optimizes both the electrical contact properties and the overall bolometer performance
2Reliability
If semiconducting single-walled carbon nanotubes are extracted using ionic surfactant to achieve uniform chirality, then TCR is improved to −2.6%/K, but manufacturing complexity increases
Solution Approach 1:
The patent changes the purification approach by using nonionic surfactants instead of ionic surfactants for carbon nanotube separation. This parameter change in surfactant type simplifies the manufacturing process while maintaining effective separation of semiconducting carbon nanotubes, reducing manufacturing complexity compared to ionic surfactant methods that require more stringent processing conditions
Solution Approach 2:
The patent employs disposable nonionic surfactants that can be easily removed or degraded after serving their separation function. These surfactants are designed to be water-soluble and environmentally benign, allowing for simple wash-away removal without requiring complex purification steps, thereby reducing overall manufacturing complexity
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 results in bolometers with reduced resistance and enhanced TCR, particularly in high voltage regions, facilitating the development of low-cost and high-performance infrared sensors.
Implementation Method 1
one or both of the two electrodes comprises a monometal or alloy having lower work function than the p-type semiconducting carbon nanotubes at least in a part of the electrode
Data Source
AI summary
One object of the present invention is to provide a bolometer having low resistance.The present invention relates to a bolometer including two electrodes and a bolometer film lying between the two electrodes to connect the two electrodes, wherein the bolometer film includes semiconducting carbon nanotubes in a proportion of 90% by mass or more to the total amount of carbon nanotubes and includes p-type semiconducting carbon nanotubes, and one or both of the two electrodes include(s) a monometal or alloy having lower work function than the p-type semiconducting carbon nanotubes at least in a part of the electrode.