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 low beam current density, large beam opening angles, and uneven energy distribution, which restrict their application in micro- and nano-manufacturing, particularly for biological samples that require low voltage detection.
Innovation Solution
A method involving a metal wire placed in vacuum with active and catalyst gases, where a positive high voltage induces field-induced chemical etching and field evaporation to shape the wire into a base with a tiny tip, enhancing the surface electric field and achieving a high beam current density and small beam opening angle.
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 obtained
Solution Approach 1:
The patent applies parameter changes by controlling the temperature of the metal wire to be lower than the boiling point of active gas, and by adjusting the electric field strength to achieve field-induced chemical etching. This creates optimal conditions for forming a sharp tip with small virtual source diameter while maintaining source stability for long operation life.
Solution Approach 2:
The patent replaces conventional mechanical tip formation methods with field-induced chemical etching (FICE). By applying electric field in the presence of active gas, chemical reactions occur at the tip surface to precisely shape the metal wire into an atomically sharp tip, achieving smaller virtual source diameter than mechanical methods.
2Illumination intensity
If cold field emission electron source is used, then smaller virtual source diameter and higher brightness are achieved, but brightness deteriorates dramatically at low voltages
Solution Approach 1:
The patent changes the operational parameters by maintaining metal wire temperature below the boiling point of active gas and controlling electric field strength. This creates a unique regime where field-induced chemical etching occurs, producing tips that maintain high brightness across a wide voltage range including low voltages, thus improving adaptability.
Solution Approach 2:
The patent applies local quality by creating field-induced chemical etching specifically at the tip region where the electric field is strongest. This localized chemical reaction precisely shapes only the critical tip area, preserving the sharpness needed for high brightness while enabling low voltage operation.
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 is obtained
Solution Approach 1:
The patent merges field-induced chemical etching with field evaporation processes. The FICE shapes the tip to achieve small virtual source diameter, while the simultaneous field evaporation removes material to create the sharp apex needed for high beam current density, combining benefits of both processes.
Solution Approach 2:
The patent effectively creates a composite process by combining chemical etching (from active gas) and physical field evaporation. This composite approach produces tips with both the precision geometry for small virtual source and the sharp apex for high 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 obtained
Solution Approach 1:
The patent replaces liquid metal ion source mechanisms with solid metal wire and field-induced chemical etching. This substitution eliminates the need for liquid metal handling while achieving comparable or superior beam current density through precisely controlled chemical etching and field evaporation that create sharp tips with small virtual source diameter.
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 method produces a particle source with improved beam current density, reduced virtual source diameter, and enhanced spatial coherence, enabling more effective electron and ion beam applications in micro- and nano-technologies.
Implementation Method 1
applying a positive high voltage V to the metal wire to dissociate the active gas at the surface of the metal wire, in order to generate at a peripheral surface 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 and catalyst gas, adjusting a temperature of the metal wire, and applying a positive high voltage V to the metal wire to dissociate the active gas at the surface of the metal wire, in order to generate at a peripheral surface 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 the to evaporation field of the material for the metal wire, so that metal atoms at the wire apex 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.