Hexaboride Electron Source with Reaction Barrier Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electron sources, particularly those using hexaboride materials, face issues with tip stability and mechanical strength due to intermetallic compound formation and thermal stress, leading to potential detachment of the hexaboride tip during heating, which affects long-term reliability and brightness.
Innovation Solution
A metal tube with recesses surrounding the central axis is used to securely house a hexaboride tip, with materials like tantalum, niobium, graphite, or rhenium inserted between the tube and tip to enhance mechanical strength and prevent intermetallic compound formation, ensuring robust joining and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hexaboride tip is directly joined to metal support, then mechanical strength is reduced due to intermetallic compound formation, but joining simplicity is improved
Solution Approach 1:
A reaction barrier layer made of tungsten, molybdenum, or titanium is introduced between the hexaboride tip and metal support. This intermediary layer prevents direct contact between hexaboride and reactive metals, blocking intermetallic compound formation while maintaining structural integrity and joining simplicity.
Solution Approach 2:
The electron source employs a composite structure consisting of hexaboride tip, reaction barrier layer, and metal support. This multi-material composite design combines the low work function advantage of hexaboride with the mechanical strength of metal support, while the barrier layer prevents detrimental chemical reactions between components.
2Reliability
If hexaboride electron source is heated for flushing, then gas adsorption is removed, but thermal stress causes tip detachment
Solution Approach 1:
The reaction barrier layer serves as a thermal stress buffer between the hexaboride tip and metal support during heating cycles. This intermediary layer accommodates differential thermal expansion, reducing thermal stress concentration at the joint interface and preventing tip detachment during flushing operations.
Solution Approach 2:
The design accounts for thermal expansion differences between hexaboride and metal support materials. The reaction barrier layer with intermediate thermal expansion properties reduces thermal stress by accommodating expansion differences, enabling repeated heating cycles without joint failure.
3Use of energy by moving object
If hexaboride tip is used, then work function is reduced to 2.6 eV, but intermetallic compound formation reduces long-term stability
Solution Approach 1:
The reaction barrier layer made of tungsten, molybdenum, or titanium acts as a protective intermediary that prevents direct chemical reaction between hexaboride and metal support. This maintains the low work function surface of hexaboride while protecting against intermetallic compound formation that would compromise long-term stability.
Solution Approach 2:
The reaction barrier layer creates a chemically inert environment between the hexaboride tip and metal support, preventing unwanted chemical reactions. This inert barrier preserves the compositional stability of the hexaboride tip while maintaining its low work function properties for efficient electron emission.
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 allows for a stable, long-term operation of hexaboride electron sources with improved mechanical strength and optical axis alignment, preventing tip detachment and maintaining high brightness and resolution.
Implementation Method 1
A high electric field is applied by concentrating an external electric field E to a tip end of the W tip, and the electron e in the W tip is quantum mechanically transmitted through an effectively thinned vacuum barrier and released into the vacuum
Implementation Method 2
heats a filament of tungsten (W) processed into a hairpin shape to about 2800 K and takes out an electron e into a vacuum by causing the electron thermally excited in W solid to cross a barrier of work function Φ
Data Source
AI summary
An electron source that can be used stably for a long time even when hexaboride is used, and an electron beam device using the electron source are provided. The invention is directed to an electron source which includes a filament made of a metal, a metal tube that is fixed to the filament and has a plurality of recesses disposed at least in two axial directions so as to surround a central axis at an outer periphery, and a columnar hexaboride tip that emits an electron, is disposed so as to protrude from the inside of the metal tube to a side opposite to the filament, and is in contact with a bottom of each of the plurality of recesses of the metal tube.