CNT String Field Emission Source With Broken Tooth Structure
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Solution Overview
Problem
Existing field emission electron sources with carbon nanotubes face issues of weak mechanical connection between CNTs and the conductive base, leading to reduced performance and efficiency due to easy detachment under electric field forces and shield effects between adjacent CNTs.
Innovation Solution
A method involving the formation of a CNT string with a broken end portion, where the string is snapped using a laser beam and attached to a conductive base, enhancing mechanical strength and reducing shield effects through Joule-heating and oxidation, resulting in improved electrical and thermal conductivity and field emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If in-situ synthesis method is used to form CNTs on conductive base, then CNTs can be directly synthesized on the base, but the mechanical connection between CNTs and conductive base is weak and unreliable
Solution Approach 1:
The patent applies preliminary action by first forming a metal catalyst layer on the conductive base, then pre-assembling CNT bundles before attaching them to the base. This preliminary preparation of the catalyst layer and CNT bundles ensures strong mechanical connection while maintaining ease of manufacture, resolving the contradiction between direct synthesis and connection reliability.
2Manufacturing precision
If mechanical method is used to place single CNT on conductive base, then precise placement is possible, but controllability is less than desired due to tiny size of single CNT
Solution Approach 1:
The patent merges multiple CNTs into bundles before placement on the conductive base. This bundling approach maintains manufacturing precision while significantly improving controllability, as the bundled CNTs are much easier to handle and position than individual CNTs. The metal catalyst layer further aids in securing the bundles with strong mechanical connection.
3Productivity
If adjacent CNTs are placed close together, then field emission density increases, but shield effect between adjacent CNTs reduces field emission efficiency
Solution Approach 1:
The patent applies local quality by creating a tooth-shaped structure with broken end portions at specific locations of the CNT string. This localized modification at the emission tip reduces shield effects between adjacent CNTs while maintaining high field emission density. The broken end portions create optimal local electric field distribution, resolving the contradiction between density and efficiency.
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 method provides a firm mechanical connection between CNTs and the base, enhancing field emission efficiency and mechanical strength, with improved electrical and thermal conductivity, as evidenced by increased current density and reduced defect modes in Raman spectra.
Implementation Method 1
heating the CNT string in air by means of Joule-heating
Implementation Method 2
heating the CNT string in air by means of Joule-heating and oxidation
Implementation Method 3
The CNT string 12 is electrically connected to the anode 208 and the cathode 210
Data Source
AI summary
A field emission electron source having carbon nanotubes includes a CNT string and a conductive base. The CNT string has an end portion and a broken end portion. The end portion is contacted with and electrically connected to the surface of the conductive base. The CNTs at the broken end portion form a tooth-shape structure, wherein some CNTs protrude and higher than the adjacent CNTs. Each protruded CNT functions as an electron emitter.