TEM Stigmator Configuration for Distortion-Free Imaging
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Solution Overview
Problem
Conventional TEMs face challenges in simultaneously correcting astigmatism and linear distortion across imaging and diffraction modes without causing drift due to changes in stigmator excitation, leading to temperature drift and hysteresis issues.
Innovation Solution
A charged particle apparatus equipped with three stigmators positioned between the objective lens and the detector system, allowing independent control of astigmatism in both modes and linear distortion, eliminating the need for excitation changes between modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two stigmators are used to correct astigmatism in imaging and diffraction modes, then astigmatism correction is improved, but linear distortion arises due to different magnification in perpendicular directions
Solution Approach 1:
The patent divides the stigmation correction function into three separate stigmators positioned at different locations between the objective lens and detector system. Each stigmator handles specific aspects of astigmatism and distortion correction, allowing independent optimization of correction in imaging mode, diffraction mode, and linear distortion reduction, thereby resolving the trade-off between astigmatism correction and linear distortion.
2Measurement precision
If stigmator excitation is changed between imaging and diffraction modes to correct astigmatism, then astigmatism correction is improved, but temperature drift and hysteresis occur
Solution Approach 1:
The patent positions three stigmators between the objective lens and detector system to enable preliminary correction of both astigmatism and linear distortion before imaging or diffraction measurements are taken. This preliminary configuration allows the stigmators to be set once to handle both modes, preventing the need for excitation changes that would cause thermal drift and hysteresis effects.
3Device complexity
If one stigmator is used for astigmatism correction, then device complexity is reduced, but the ability to correct both astigmatism and linear distortion simultaneously is compromised
Solution Approach 1:
The patent applies local quality by positioning three stigmators at specific locations between the objective lens and detector system, where each stigmator has a distinct functional role. This spatial differentiation allows each stigmator to be optimized for specific correction tasks (imaging mode astigmatism, diffraction mode astigmatism, and linear distortion), providing versatile correction capability while maintaining a modular and manageable device 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
This configuration ensures zero astigmatism and linear distortion in both imaging and diffraction modes, preventing temperature drift and hysteresis, thus stabilizing the image without requiring changes in stigmator excitation when switching between modes.
Implementation Method 1
a first stigmator is positioned for reducing astigmatism when imaging a sample on the detector system and a second stigmator is positioned for reducing astigmatism when the diffraction plane is imaged on the detector system
Implementation Method 2
The objective lens forms a first image of the sample with a magnification of, for example, 20 times
Implementation Method 3
a sample, such as a thin slice of biological material or a thin slice of semiconductor material, with a thickness of typically between 2 nm to 1 μm, is irradiated with an energetic beam of electrons
Data Source
AI summary
A charged particle apparatus is equipped with a third stigmator positioned between the objective lens and a detector system, as a result of which a third degree of freedom is created for reducing the linear distortion. Further, a method of using said three stigmators, comprises exciting the first stigmator to reduce astigmatism when imaging the sample, exciting the second stigmator to reduce astigmatism when imaging the diffraction plane, and exciting the third stigmator to reduce the linear distortion.