Mirror Monochromator for Electron Beam Energy Spread Reduction
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Solution Overview
Problem
Current electron microscopes and beam patterning systems face limitations in achieving high spatial resolution due to finite energy spread of the electron beam, leading to chromatic aberrations, which are exacerbated at lower beam energies, and existing monochromator designs are complex and prone to contamination.
Innovation Solution
An electron mirror-based monochromator using a prism separator and knife-edge plate to selectively remove energy tails from the electron beam, achieving a nearly monochromatic beam with an energy spread of 0.1 eV or less, simplifying the design and improving reliability under electron bombardment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional monochromator designs (Wien filter, omega filter) are used to reduce energy spread, then energy spread can be reduced to 0.1 eV or less, but device complexity increases and reliability decreases due to hydrocarbon contamination from narrow slits
Solution Approach 1:
The patent extracts the energy filtering function from complex slit-based monochromators and implements it using an electron mirror with a simple aperture. The electron mirror reflects electrons based on their energy, allowing the high-energy tail to be blocked by a simple aperture while transmitting the monochromatic beam, thereby achieving energy filtering without complex narrow slits that are prone to contamination.
Solution Approach 2:
The patent uses an electron mirror that creates a virtual image of the electron source at a different position. By placing the aperture in the reflected beam path, the system effectively copies the filtering function to a location where a simple aperture suffices, rather than requiring complex slits at the source location.
2Manufacturing precision
If traditional monochromator designs (Wien filter, omega filter) are used to reduce energy spread, then energy spread can be reduced to 0.1 eV or less, but device complexity increases
Solution Approach 1:
The patent extracts the energy filtering function from complex slit-based monochromators and implements it using an electron mirror with a simple aperture. The electron mirror reflects electrons based on their energy, allowing the high-energy tail to be blocked by a simple aperture while transmitting the monochromatic beam, thereby achieving energy filtering without complex narrow slits.
Solution Approach 2:
The patent replaces the mechanical slit-based filtering system with an electron mirror-based optical system. Instead of using physical slits to filter electrons, the system uses the electron mirror's ability to reflect electrons at different angles based on their energy, combined with a simple aperture, to achieve the same filtering effect with much lower mechanical complexity.
3Manufacturing precision
If beam energy is reduced to achieve better resolution, then spatial resolution improves, but chromatic aberrations increase due to finite energy spread
Solution Approach 1:
The patent applies preliminary action by reducing the energy spread of the electron beam to 0.1 eV or less using the electron mirror monochromator before the beam interacts with the specimen. This preliminary energy filtering ensures that when low-energy electrons are used for high-resolution imaging, the chromatic aberrations are minimized because the energy spread is already reduced in advance.
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 approach significantly reduces chromatic aberrations, enhancing spatial resolution in electron microscopes and patterning systems, particularly at low beam energies, and simplifies the design and manufacturing process compared to traditional monochromators.
Implementation Method 1
the beam separator introduces an angular dispersion that disperses the incoming electron beam according to its energy
Implementation Method 2
An electron lens is configured to focus the electron beam into an electron mirror so that after the reflection, the other energy tail is stopped on the same knife-edge plate
Data Source
AI summary
One embodiment relates to an apparatus for generating a charged particle beam with reduced energy width. A charged particle source is configured to generate a charged particle beam with a range of energies. An energy-dispersive device bends the high-energy component of the charged particle beam at less of an angle in comparison to the bending angle of the low-energy component of the charged particle beam, such that the higher and lower energy charged particle beam components exit the energy-dispersive device at different angles of trajectory. A charged particle mirror reflects the charged particle beam such that charged particles entering at an angle with respect to the normal to the mirror reflection plane exit the mirror symmetrically with respect to the normal and at the same angle. Charged particle lenses converge all energy components exiting the energy-dispersive device at different angles of trajectory at the charged particle mirror reflection plane. A knife-edge plate removes all charged particles with energies higher and lower than a selected energy width. Other embodiments are also disclosed.