Cold Cathode Field-Emission Electron Gun With Biased Electrode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cold cathode field-emission electron guns experience a decline in brightness and an increase in energy spread due to interelectronic interaction, which affects the performance of electron microscopes by reducing the quality of the electron beam.
Innovation Solution
Incorporating a biased electrode closer to the emitter than the extraction electrode, with a variable voltage applied to it, allows for the strengthening of the electric field between the emitter and the extraction electrode, reducing interelectronic interaction effects by enabling higher extracting voltage while maintaining a desired electric field strength on the emitter's surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the tip of the emitter is sharpened to concentrate the electric field, then a strong surface electric field is realized, but the electrons are accelerated relatively gradually resulting in interelectronic interaction
Solution Approach 1:
The patent divides the electron acceleration process into two stages by introducing a biased electrode: (1) electron emission from the emitter tip under strong electric field, and (2) electron acceleration in the region between the biased electrode and extraction electrode. This segmentation allows the electric field to be concentrated at the emitter tip for emission while providing a separate acceleration region that increases electron speed before the electrons interact with each other.
Solution Approach 2:
The patent introduces a new spatial dimension by placing a biased electrode between the emitter and extraction electrode, creating a three-region structure (emitter-biased electrode-extraction electrode). This additional dimension allows independent control of the electric field at the emitter surface and the acceleration field in the extraction region, resolving the contradiction between field concentration and acceleration speed.
2Quantity of substance
If a strong electric field is applied to the emitter surface for electron emission, then electron emission is enhanced, but interelectronic interaction increases causing brightness decline and energy spread increase
Solution Approach 1:
The patent segments the electric field function into two distinct regions: the emitter-biased electrode region for electron emission and the biased electrode-extraction electrode region for electron acceleration. This allows high electron emission current to be achieved at the emitter surface while simultaneously providing rapid acceleration in the second region that reduces electron transit time and minimizes interelectronic interaction, thereby maintaining beam quality.
Solution Approach 2:
The biased electrode performs a preliminary acceleration action on electrons immediately after emission, increasing their speed before they can interact significantly with other electrons. This preliminary acceleration reduces the time electrons spend in the high-current-density region, preventing brightness decline and energy spread increase while maintaining high emission current.
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 enhances electron acceleration, reduces energy spread, and maintains brightness, thereby improving the performance of the electron gun and electron microscope by controlling the electric fields effectively.
Implementation Method 1
causing the biased electrode and the extraction electrode to form an electric field for causing electrons to be emitted from a tip of the emitter and an electric field for accelerating the electrons emitted from the emitter between the emitter and the extraction electrode
Implementation Method 2
A cold cathode field-emission electron gun is an electron gun which applies a strong electric field to an emitter at room temperature to cause the emitter to emit electrons due to a tunnel effect
Data Source
AI summary
A cold cathode field-emission electron gun includes: an emitter; an extraction electrode which extracts electrons from the emitter; and a biased electrode which is disposed closer to the emitter than the extraction electrode. A voltage applied to the biased electrode is variable.