Field Emission Cathode with Oriented Carbon Nanotube Bundles
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for fabricating carbon nanotube field emission cathodes face issues with entangled nanotubes, low emitter density, damage during processing, and high costs, resulting in unsatisfactory field emission characteristics and efficiency.
Innovation Solution
A method involving a conductive substrate with a super-aligned carbon nanotube film, where carbon nanotube bundles are oriented parallel and partially extrude, formed by growing carbon nanotubes on a substrate and adhering them using van der Waals forces, with optional additional silver paste for stability, to create a stable and efficient field emission cathode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If in-situ synthesis method is used to grow carbon nanotubes on cathode electrode, then carbon nanotubes can be directly formed on the electrode surface, but the carbon nanotubes entangle with each other resulting in unsatisfactory field emission characteristics
Solution Approach 1:
The patent segments the carbon nanotube structure into multiple components: a vertically aligned carbon nanotube array grown on a substrate, and a separate conductive cathode electrode. This segmentation prevents entanglement by maintaining spatial separation between the nanotube growth substrate and the final cathode assembly, thereby preserving field emission characteristics while keeping the manufacturing process simple.
Solution Approach 2:
The patent introduces an intermediary substrate as a mediator between the carbon nanotube synthesis process and the final cathode assembly. The substrate serves as a temporary platform for growing well-ordered nanotubes, which are then transferred to the cathode electrode. This intermediary approach eliminates direct entanglement issues while maintaining ease of manufacture through standard CVD techniques.
2Reliability
If printing method is used to form carbon nanotube pattern on cathode electrode, then carbon nanotube emitters can be formed by extrusion, but the density of effective emitters is low and carbon nanotubes entangle and are oblique to the electrode
Solution Approach 1:
The patent applies preliminary action by pre-growing a dense, vertically aligned carbon nanotube array on a substrate before transferring it to the cathode electrode. This pre-formed structure ensures high emitter density and proper orientation are achieved during the growth stage, eliminating the need for complex post-growth extrusion and peeling processes that reduce density and increase device complexity.
3Reliability
If printing method with peeling step is used to form extrusions, then carbon nanotube emitters can be created, but the peeling step damages carbon nanotubes and decreases their performance
Solution Approach 1:
The patent extracts the damaging peeling step from the manufacturing process by using a transfer method where the carbon nanotube array is lifted off the substrate intact and transferred to the cathode electrode. This extraction eliminates mechanical damage to the nanotubes during processing, preserving their performance while maintaining ease of manufacture through a simplified two-step process of growth and transfer.
4Reliability
If printing method is used to fabricate field emission cathode, then carbon nanotube patterns can be formed, but the cost is relatively high
Solution Approach 1:
The patent employs a disposable substrate approach where a low-cost substrate is used temporarily for growing the carbon nanotube array. After the nanotubes are grown and transferred to the cathode electrode, the substrate is discarded. This strategy reduces overall manufacturing cost by using inexpensive, single-use substrates instead of expensive reusable equipment or complex processing steps, while maintaining high field emission performance.
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 approach results in a field emission cathode with improved stability, high efficiency, and low cost, as the carbon nanotube film maintains mechanical strength and exhibits significant current increase above 150V, with enhanced controllability and electron emission performance.
Implementation Method 1
adhering them using van der Waals forces
Data Source
AI summary
A field emission cathode includes a conductive substrate and a carbon nanotube film disposed on a surface of the conductive substrate. The carbon nanotube film includes a plurality of successive and oriented carbon nanotube bundles parallel to the conductive substrate, the carbon nanotubes partially extrude from the carbon nanotube film. A method for fabricating the field emission cathode includes the steps of: (a) providing a conductive substrate; (b) providing at least one carbon nanotube film, the carbon nanotube film including a plurality of successive and oriented carbon nanotube bundles joined end to end, the carbon nanotube bundles parallel to the conductive substrate, and (c) disposing the at least one carbon nanotube film to the conductive substrate to achieve the field emission cathode.