TEM Sample Alignment via Diffraction Asymmetry
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Solution Overview
Problem
Current methods for aligning a sample in a transmission electron microscope (TEM) require specialized knowledge of crystallography and tilting behavior, are time-consuming, and expose sensitive materials to the electron beam excessively, leading to potential damage and inaccurate alignment due to structure factors and dynamic effects.
Innovation Solution
An automated system and method that uses an electron beam to determine the sample's orientation relative to the zone axis based on the distribution of reflections in the image, adjusting the sample's orientation using a processor-controlled sample holder to minimize exposures and avoid structure factor influences, with the processor calculating tilt adjustments from the zero-order Laue circle radius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual alignment process is used with operator understanding of crystallography, then alignment accuracy can be achieved, but the process becomes time-consuming and requires specialized knowledge
Solution Approach 1:
The system enables automatic alignment by having the computer control the sample holder tilting based on diffraction pattern analysis, eliminating the need for manual operator intervention. The system serves itself by automatically calculating tilt corrections and executing the alignment process without requiring specialized crystallographic knowledge from an operator.
Solution Approach 2:
The patent replaces the manual mechanical alignment process with an automated computer-controlled system. The computer calculates tilt corrections based on diffraction pattern asymmetry and automatically controls the sample holder, substituting human mechanical adjustment with automated computational control.
2Measurement precision
If multiple electron beam exposures are performed for alignment confirmation, then alignment accuracy is improved, but sample damage increases due to cumulative electron dose
Solution Approach 1:
The system uses feedback from the diffraction pattern intensity asymmetry to automatically determine and apply tilt corrections. By monitoring the asymmetry metric in real-time during the alignment process, the system can achieve accurate alignment with minimal exposures, reducing sample damage while maintaining precision through continuous feedback control.
Solution Approach 2:
The patent applies just enough electron beam exposure to obtain the necessary diffraction pattern information for alignment, avoiding excessive exposures. The system calculates the minimum required tilts based on asymmetry analysis, performing only the necessary action to achieve alignment without over-exposing the sample.
3Extent of automation
If computer-assisted tool using intensity asymmetry is used, then automation is improved, but alignment accuracy deteriorates due to structure factors and dynamic effects
Solution Approach 1:
The patent extracts and eliminates the harmful influence of structure factors and dynamic effects from the alignment calculation. By using a different metric (intensity asymmetry) that is not affected by these factors, the system takes out the problematic elements that cause inaccurate alignment in conventional intensity-based methods.
Solution Approach 2:
The system changes the parameter used for alignment determination from diffraction intensity to intensity asymmetry. This parameter change makes the alignment process immune to structure factors and dynamic effects, as asymmetry is a geometric property of the diffraction pattern that remains valid regardless of these physical effects.
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 allows for accurate and efficient zone axis alignment with reduced electron beam exposure, minimizing sample damage and achieving precise alignment without requiring in-depth crystallographic knowledge, enabling higher-resolution studies with lower electron doses.
Implementation Method 1
applying an electron beam having a wavelength λ to a sample... based on a distribution of reflections in the image
Data Source
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AI summary
A system and method involve applying an electron beam to a sample and obtaining an image of the sample with the applied electron beam. An orientation of the sample relative to the sample's zone axis is automatically determined based on a distribution of reflections in the image. The orientation of the sample is automatically adjusted to align with the sample's zone axis based on the determined orientation.