STEM Aperture Alignment Using Voltage-Shifted Image Comparison
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Solution Overview
Problem
Existing scanning transmission electron microscopes require frequent adjustment of the aperture alignment with the Ronchigram center, necessitating formation of the Ronchigram in an amorphous region of the specimen each time, which is inefficient and prone to drift issues.
Innovation Solution
A method and apparatus for aligning the aperture in a scanning transmission electron microscope that utilizes a control unit to maintain the optical system's image center at the Ronchigram center despite fluctuations in acceleration voltage or excitation current, allowing alignment based on position deviations between STEM images taken at different voltage or current settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the aperture is aligned by inserting it and checking the Ronchigram each time, then the alignment precision is improved, but the operation time and complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-acquiring Ronchigram images at multiple acceleration voltages before alignment. These pre-acquired images are stored and later used for automated alignment comparison, eliminating the need to form Ronchigrams repeatedly during alignment operations. This reduces both time and operational complexity while maintaining precision.
Solution Approach 2:
The patent uses copying by creating digital copies of Ronchigram images at different acceleration voltages. These copied images are stored in memory and used for comparison during alignment. Instead of repeatedly forming new Ronchigrams, the system compares digital copies, significantly reducing the time and effort required for alignment while maintaining measurement precision.
2Measurement precision
If the Ronchigram is formed in the amorphous region of the specimen each time, then the alignment accuracy is improved, but the productivity decreases
Solution Approach 1:
The system performs preliminary acquisition of Ronchigram images at various acceleration voltages before the actual alignment process. These pre-acquired images are stored and reused during alignment, eliminating the need to repeatedly form Ronchigrams in the amorphous region. This maintains alignment accuracy while significantly improving productivity by reducing repetitive operations.
Solution Approach 2:
The patent creates digital copies of Ronchigram images obtained from the amorphous region at different acceleration voltages. These copied images are stored in memory and used for automated comparison during alignment. This approach maintains the accuracy benefits of using the amorphous region while improving productivity by avoiding repeated formation of Ronchigrams.
3Stability of the object's composition
If the aperture alignment is adjusted frequently, then the image stability is improved, but the operation complexity increases
Solution Approach 1:
The patent implements feedback by automatically comparing the captured Ronchigram image with pre-acquired reference images at different acceleration voltages. The system calculates position deviations and automatically determines the optimal aperture alignment position. This automated feedback loop maintains image stability while reducing operational complexity by eliminating manual adjustment procedures.
Solution Approach 2:
The system performs self-service by automatically acquiring Ronchigram images, comparing them with reference images, calculating position deviations, and determining the optimal aperture alignment position without operator intervention. This self-aligning capability maintains image stability while significantly reducing operational complexity.
4Measurement precision
If the aperture is aligned manually by checking the Ronchigram, then the measurement precision is improved, but the ease of operation deteriorates
Solution Approach 1:
The patent uses feedback by automatically comparing captured Ronchigram images with pre-acquired reference images and calculating position deviations. The system provides automated alignment recommendations based on this feedback, maintaining high precision while eliminating the need for manual checking and adjustment, thereby improving ease of operation.
Solution Approach 2:
The patent replaces the manual mechanical alignment process with an automated image processing system. Instead of manually adjusting the aperture while visually checking the Ronchigram, the system uses computer-controlled image acquisition, digital image comparison, and automated position calculation. This substitution maintains alignment precision while dramatically improving ease of operation.
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
Enables easy and precise alignment of the aperture with the Ronchigram center without the need for continuous Ronchigram observation, reducing drift and simplifying the alignment process.
Implementation Method 1
an electron source that generates an electron beam; an optical system that has a condenser lens, an aperture, and an objective lens and forms an electron probe by condensing the electron beam generated by the electron source
Data Source
Figure 1
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AI summary
A scanning transmission electron microscope includes an electron source that generates an electron beam, an optical system that has a condenser lens, an aperture, and an objective lens and forms an electron probe by condensing the electron beam generated by the electron source, and a control unit that controls the electron source and the optical system, the optical system being in a state in which an image is not moved at a center of a Ronchigram even when an acceleration voltage for accelerating the electron beam is fluctuated, and the control unit performing processing of: inserting the aperture into a path of the electron beam; setting the acceleration voltage to a first voltage value and obtaining a first STEM image, in a state in which the aperture is inserted; setting the acceleration voltage to a second voltage value that is different from the first voltage value and obtaining a second STEM image, in a state in which the aperture is inserted; and moving the aperture based on position deviation between the first STEM image and the second STEM image.