STEM Ronchigram Alignment Without Specimen Stage Tilting
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Solution Overview
Problem
Tilting the specimen stage in a scanning transmission electron microscope (STEM) causes drift due to backlash and other effects, making it difficult to align the electron beam with the crystal zone axis accurately.
Innovation Solution
An image acquisition method and scanning transmission electron microscope design that aligns the electron beam with the crystal zone axis by adjusting the shadow of the condenser aperture on the diffraction plane using illumination and imaging system deflectors, without tilting the specimen stage, and controls the electron beam to align with the detector plane center.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the specimen stage is tilted to align the crystal zone axis with the electron beam direction, then the alignment accuracy is improved, but specimen drift occurs due to backlash and other effects
Solution Approach 1:
The patent replaces the mechanical tilting of the specimen stage with electromagnetic deflection of the electron beam using deflectors. Instead of physically moving the specimen to achieve alignment, the electron beam is electronically steered to match the crystal zone axis, thereby eliminating backlash-induced drift while maintaining alignment precision.
Solution Approach 2:
Rather than tilting the specimen to align with the fixed electron beam, the patent inverts the approach by keeping the specimen stationary and tilting the electron beam direction through deflector control. This reversal eliminates the mechanical instability associated with specimen stage tilting.
2Adaptability or versatility
If the electron beam is deflected to align with the crystal zone axis, then the alignment flexibility is improved, but the beam position accuracy may deteriorate
Solution Approach 1:
The patent employs feedback control where the deflected electron beam position is monitored (e.g., using a Ronchigram or detector), and the deflector parameters are adjusted based on this feedback to maintain precise alignment with the crystal zone axis. This closed-loop control ensures both flexibility and accuracy.
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 reduces specimen drift and aberration, enabling high-resolution imaging of crystalline specimens by maintaining focus and reducing changes in specimen height during scanning.
Implementation Method 1
an illumination system deflector that deflects the electron beam having passed through the aperture
Implementation Method 2
an imaging system deflector that deflects the electron beam to be incident on the imaging apparatus
Implementation Method 3
an illumination system including a condenser lens, an aperture, and an illumination system deflector
Implementation Method 4
an electron source that emits an electron beam
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An image acquisition method of acquiring an image of a crystalline specimen in a scanning transmission electron microscope (100) that includes: an electron source (11) configured to emit an electron beam; an illumination system (2) including a condenser lens (12), an aperture, an illumination system deflector (14) configured to deflect the electron beam having passed through the aperture, and an objective lens (16); a specimen stage (20) configured to support the specimen; an imaging apparatus (30) capable of photographing a Ronchigram formed on a diffraction plane of the objective lens (16); and an imaging system deflector (18) configured to deflect the electron beam to be incident on the imaging apparatus (30), includes the steps of: aligning a center of the Ronchigram with a center of a detector plane (32) of the imaging apparatus (30); aligning a direction of incidence of the electron beam with respect to the specimen with a crystal zone axis of the specimen by aligning a shadow of the aperture with the crystal zone axis on the diffraction plane; and causing the imaging system deflector (18) to deflect the electron beam to align the electron beam with the center of the detector plane (32) of the imaging apparatus (30).