Cold-Field Emitter Extractor Self-Cleaning by Reversed E-Beam
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Solution Overview
Problem
Residual gas pressure in extreme ultra-high vacuum environments contaminates the extractor electrode of cold-field emission sources, shortening their lifetime and introducing emission noise, despite bakeout processes.
Innovation Solution
A method involving a reversible biasing of the extractor electrode and mirror electrode in an e-beam device, where the mirror electrode acts as a mirror to reflect electrons back onto the extractor electrode, utilizing Desorption Induced by Electronic Transition (DIET) to clean and anneal the electrode surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the extractor electrode is baked out to reduce outgassing, then the vacuum quality is improved, but molecules remain adsorbed on the extractor electrode surface near the cold-field emission source
Solution Approach 1:
The invention uses the electron beam, which is necessary for the device operation, to clean the extractor electrode surface. The electron beam irradiates the surface during normal operation, causing desorption of adsorbed molecules and converting the potentially harmful electron beam into a beneficial cleaning mechanism that prevents contamination buildup.
Solution Approach 2:
The system performs self-cleaning of the extractor electrode using its own electron beam during normal operation. The electron beam automatically irradiates the extractor surface, causing continuous desorption of adsorbed species without requiring external intervention or separate cleaning processes.
2Productivity
If the extractor electrode is positively biased to extract electrons, then electron emission is improved, but contaminant monolayer forms on the extractor surface
Solution Approach 1:
The electron beam cleaning action continues continuously during normal device operation. As electrons are extracted through the positively biased extractor, the same electron beam continuously irradiates the extractor surface, maintaining a clean state and preventing contaminant monolayer formation throughout the operational lifetime of the device.
Solution Approach 2:
The electron beam that could potentially contribute to contamination is instead utilized to clean the surface. The high-energy electrons in the beam cause desorption of adsorbed species, converting what could be a contamination source into a self-cleaning mechanism that operates concurrently with electron extraction.
3Ease of manufacture
If bakeout is used to clean the extractor electrode, then some desorption is achieved, but complete removal of adsorbed molecules near the emission source is insufficient
Solution Approach 1:
The invention replaces thermal processing (bakeout) with electronic processing (electron beam irradiation) for cleaning the extractor electrode. The electron beam provides a more effective cleaning mechanism that directly removes adsorbed molecules through electronic transitions, achieving superior cleaning results compared to thermal methods alone.
Solution Approach 2:
The cleaning mechanism transitions from thermal energy (bakeout at elevated temperatures) to electronic energy (electron beam irradiation). This parameter change enables more effective desorption of adsorbed molecules, particularly near the cold-field emission source where thermal gradients and outgassing are most problematic.
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 method effectively removes chemisorbed radicals and minimizes steady-state outgassing, enhancing the lifetime and performance of the cold-field emission source by preventing the formation of a monolayer of contaminants.
Implementation Method 1
utilizing Desorption Induced by Electronic Transition (DIET) to clean and anneal the electrode surfaces
Implementation Method 2
cold-field emission source to emit electrons and an extractor electrode to be positively biased with respect to the cold-field emission source to extract the electrons
Implementation Method 3
the mirror electrode acts as a mirror to reflect electrons back onto the extractor electrode
Implementation Method 4
clean and anneal the electrode surfaces
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An e-beam device includes a cold-field emission source to emit electrons and an extractor electrode to be positively biased with respect to the cold-field emission source to extract the electrons from the cold-field emission source. The extractor electrode has a first opening for the electrons. The e-beam device also includes a mirror electrode with a second opening for the electrons. The mirror electrode is configurable to be positively biased with respect to the extractor electrode during a first mode of operation and to be negatively biased with respect to the extractor electrode during a second mode of operation. The extractor electrode is disposed between the cold-field emission source and the mirror electrode. The e-beam device further includes an anode to be positively biased with respect to the extractor electrode and the coldfield emission source. The mirror electrode is disposed between the extractor electrode and the anode.