Tapered Wire Emitter for Liquid Metal Ion Sources
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Solution Overview
Problem
Existing liquid metal ion sources, such as needle-type and capillary-type emitters, face inefficiencies due to indirect heating, potential evaporation of source material, and complexity in manufacturing, leading to reduced emitter lifetime and increased contamination in focused ion beam technology.
Innovation Solution
A wire-based emitter with a substantially curved portion, tapered to form a pointed tip, allowing direct heating and improved temperature distribution, eliminating the need for welding and simplifying the structure, while facilitating the use of alloys with poor wetting properties and high melting points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If needle-type emitter with welding is used, then emitter structure is formed, but indirect heating causes temperature distribution issues and source material evaporation
Solution Approach 1:
The patent merges the filament and needle tip into a single integrated wire structure, eliminating the welding connection between separate components. This integration ensures direct heating of the tip region and eliminates thermal resistance at the weld interface, resolving the temperature distribution issues while maintaining structural integrity.
Solution Approach 2:
The wire is designed with segmented functional regions including a curved portion, a tapered portion with varying diameter, and a tip portion. This segmentation allows different regions to serve specific functions: the curved portion provides mechanical support, the tapered portion creates thermal gradient, and the tip portion generates the ion beam, thereby optimizing temperature distribution.
2Quantity of substance
If capillary-type emitter is used, then source material reservoir is provided, but complex manufacturing process is required
Solution Approach 1:
The wire surface is designed with porous structure that allows liquid source material to be absorbed and retained within the porous network. This eliminates the need for complex capillary structures while providing adequate source material reservoir, significantly simplifying the manufacturing process.
3Temperature
If tapered wire structure is used, then direct heating and temperature control is improved, but manufacturing precision is required
Solution Approach 1:
The wire diameter is varied continuously along its length to create the tapered structure, with the diameter decreasing from the curved portion toward the tip. This parameter change creates a thermal gradient that concentrates heat at the tip region, improving temperature control while the gradual transition reduces manufacturing difficulty compared to sharp geometric features.
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 solution enhances the emitter's lifetime, reduces contamination, and improves the stability of the ion beam by ensuring the emitter tip is the hottest part, allowing efficient operation with high melting point materials and alloys, and simplifying the manufacturing process.
Implementation Method 1
The emitter includes a wire, the wire including: a substantially curved portion and a surface, wherein at least a portion of the wire surface is tapered at the substantially curved portion to form an emitter tip
Implementation Method 2
The heated liquid metal flows towards the needle-tip. High voltage is then applied between the needle tip and an extraction electrode. Due to the high electric field strength at the needle tip, an even smaller tip of liquid source material forms a so-called Taylor cone from which the ions are emitted
Implementation Method 3
During operation, electric current is supplied to the filaments which are thus resistively heated
Implementation Method 4
High voltage is then applied between the needle tip and an extraction electrode. Due to the high electric field strength at the needle tip, an even smaller tip of liquid source material forms a so-called Taylor cone from which the ions are emitted
Data Source
AI summary
An emitter for a liquid metal ion source is provided. The emitter includes a wire comprising a substantially curved portion and a surface wherein at least a portion of the wire surface is tapered at the substantially curved portion to form an emitter tip. Furthermore, a manufacturing method for such an emitter is provided.