Particle Source Tip Shaping via Field-Induced Chemical Etching
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Solution Overview
Problem
Current particle sources for electronic microscopes and focused ion beam systems face limitations such as larger virtual source diameter, lower resolution, and uneven energy distribution, which restrict their application in micro- and nano-technology, particularly in detecting biological samples at low voltages and in focused ion beam systems.
Innovation Solution
A method involving field-induced chemical etching (FICE) and field evaporation is used to shape a metal wire into a particle source with a small tip and large base, creating a high beam current density and small beam opening angle, by applying a positive high voltage in a vacuum environment with active gas, controlling temperature, and adjusting the etching zone to achieve a predetermined shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If Schottky field emission electron source is used, then long life time is achieved, but larger virtual source diameter and lower resolution are resulted
Solution Approach 1:
The patent applies field-induced chemical etching (FICE) to modify the physical and chemical parameters of the metal wire surface, transforming it into a sharp tip structure with different surface properties. This parameter change enables the wire to achieve cold field emission characteristics (small virtual source diameter) while maintaining structural integrity for long operation
Solution Approach 2:
The patent replaces conventional thermal field emission mechanisms with cold field emission by substituting the heating mechanism with an electric field-induced chemical etching mechanism. This substitution allows the metal wire to form a sharp tip that emits electrons via quantum tunneling at room temperature, achieving small virtual source diameter without thermal broadening
2Manufacturing precision
If cold field emission electron source is used, then smaller virtual source diameter and higher brightness are achieved, but brightness varies dramatically at low voltages which is not suitable for biological samples
Solution Approach 1:
The patent modifies the surface chemical composition and morphology of the metal wire through FICE, creating a tip structure with optimized work function and field enhancement characteristics. This parameter optimization enables stable electron emission across a wide voltage range including low voltages suitable for biological sample imaging
3Manufacturing precision
If Gas field ion source is used, then smaller virtual source diameter and uniform ion energy distribution are achieved, but very low beam current density restricts application in micro- and nano-manufacture
Solution Approach 1:
The patent merges the advantages of field-induced chemical etching (which creates uniform sharp tips for small virtual source diameter) with field evaporation (which provides high ion beam current density). The combination of these two field-based mechanisms produces metal ion sources that simultaneously achieve small virtual source diameter, uniform energy distribution, and high beam current density
4Quantity of substance
If liquid metal ion source is used, then high beam current density is achieved, but larger virtual source diameter and uneven ion energy distribution are resulted
Solution Approach 1:
The patent replaces the liquid metal jet mechanism with a solid metal wire tip subjected to field-induced chemical etching and field evaporation. This substitution eliminates the inherent virtual source diameter limitations of liquid metal sources while maintaining high ion current density through controlled field emission from the etched tip structure
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 resulting particle source achieves high beam current density, small beam opening angle, reduced virtual source diameter, and improved electron energy distribution, enabling better spatial coherence and increased application in micro- and nano-technologies.
Implementation Method 1
applying a positive high voltage V to the metal wire to generate at a side of the head of the metal wire an etching zone in which field induced chemical etching (FICE) is performed
Implementation Method 2
increasing by the FICE a surface electric field at the top of the metal wire head to be greater than a field evaporation electric field of material for the metal wire, so that metal atoms at the top of the metal wire are evaporated off
Data Source
AI summary
The present disclosure provides a method for manufacturing a particle source comprising: placing a metal wire in vacuum, introducing active gas, adjusting a temperature of the metal wire and applying a positive high voltage V to the metal wire to generate at a side of the head of the metal wire an etching zone in which field induced chemical etching (FICE) is performed; increasing by the FICE a surface electric field at the top of the metal wire head to be greater than a field evaporation electric field of material for the metal wire, so that metal atoms at the top of the metal wire are evaporated off; after the field evaporation is activated by the FICE, causing mutual adjustment between the FICE and the field evaporation, until the head of the metal wire has a shape of combination of a base and a tip on the base; and stopping the FICE and the field evaporation when the head of the metal wire takes a predetermine shape.