Field Emission Device Secondary Electron Layer Ion Protection
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Solution Overview
Problem
Field emission devices suffer from a short lifespan due to ion bombardment of carbon nanotubes, which causes damage and reduces their effectiveness in field emission displays.
Innovation Solution
A field emission device design that includes a secondary electron emission layer and a protective layer on the electron emission tips, positioned to minimize ion bombardment by ensuring electrons collide with the secondary electron emission layer before gas molecules, thereby reducing ionization and extending the lifespan of the carbon nanotubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbon nanotubes are exposed through holes in the dielectric layer to enable electron emission, then field emission performance is improved, but the carbon nanotubes are bombarded by ions causing damage and short lifespan
Solution Approach 1:
A protective layer is introduced as an intermediary between the carbon nanotubes and the ion bombardment environment. This protective layer absorbs the harmful ion impact while allowing the carbon nanotubes to continue emitting electrons effectively, thus resolving the contradiction between maintaining emission performance and extending tube lifespan.
Solution Approach 2:
The patent operates the field emission device in a vacuum or inert gas environment to prevent ionization of gas molecules. By eliminating or reducing the presence of ionizable gas molecules, the harmful ion bombardment is minimized, allowing the exposed carbon nanotubes to maintain both high emission performance and extended operational lifespan.
2Power
If electrons are emitted from carbon nanotubes and accelerated toward the anode, then current flow is improved, but electrons ionize gas molecules producing ions that bombard and damage the carbon nanotubes
Solution Approach 1:
By maintaining a vacuum or inert gas atmosphere, the patent prevents gas molecules from being ionized by the accelerated electrons. This eliminates the harmful ion bombardment effect while preserving the electron current flow from the carbon nanotubes to the anode, thus resolving the contradiction between power output and harmful ion generation.
Solution Approach 2:
The protective layer serves as a mediator that intercepts ions before they can reach the carbon nanotubes. This allows high current flow to be maintained while the protective layer absorbs the ion bombardment damage, protecting the electron emitting structures.
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 design enhances the lifespan of the electron emitters and increases emission current by reducing ion bombardment, while maintaining operation in vacuum or inert gas environments without damage.
Implementation Method 1
When a voltage is applied between the anode electrode and the cathode electrode, a number of electrons are emitted from the carbon nanotubes and strike the anode electrode through the holes
Implementation Method 2
the electrons collide with free gas molecules in the vacuum and ionize the free gas molecules, thereby producing ions
Data Source
AI summary
A method for making a field emission device includes the following steps. An insulative substrate is provided. An electron pulling electrode is formed on the insulative substrate. A secondary electron emission layer is formed on the electron pulling electrode. A first dielectric layer is fabricated. The first dielectric layer has a second opening to expose the secondary electron emission layer. A cathode plate having an electron output portion is provided. An electron emission layer is formed on part surface of the cathode plate. The cathode plate is placed on the first dielectric layer. The electron output portion and the second opening have at least one part overlapped, and at least one part of the electron emission layer is oriented to the secondary electron emission layer via the second opening.