Scanning Transmission Electron Microscope Atomic Resolution
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Solution Overview
Problem
Conventional scanning transmission electron microscopes struggle to achieve atomic resolution and three-dimensional imaging of specimens, particularly in identifying internal structures and atomic positions due to limitations in image resolution and depth direction signal projection.
Innovation Solution
The implementation of an electron lens system with a small spherical aberration coefficient, an aperture for varying illumination angles, and a combination of secondary electron and forward scattered electron detectors, along with image processing for three-dimensional reconstruction, enables atomic size three-dimensional observation and identification of specimen structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional scanning transmission electron microscope uses transmission electrons or forward scattered electrons for imaging, then image formation is achieved, but atomic resolution and three-dimensional structural information cannot be obtained due to signal superposition from depth direction
Solution Approach 1:
The patent segments the electron signal detection into multiple channels: secondary electron detector for surface/depth-resolved imaging, forward scattered electron detector for internal structure, and transmission electron detector for transmitted signal. This segmentation allows separate detection of electrons from different depths and scattering angles, enabling three-dimensional structural information to be extracted without signal superposition.
Solution Approach 2:
The patent adds depth direction information by detecting secondary electrons at different emission angles and combining them with forward scattered and transmission electron signals. This transforms the conventional two-dimensional projection imaging into three-dimensional structural visualization by incorporating the depth dimension through angularly resolved secondary electron detection.
2Measurement precision
If electron beam spot size is reduced to achieve atomic resolution, then image resolution improves, but spherical aberration and other optical aberrations worsen
Solution Approach 1:
The patent merges multiple detection modalities (secondary electron detection, forward scattered electron detection, and transmission electron detection) into a single imaging system. This combination allows the system to overcome the limitations of each individual method: secondary electrons provide surface sensitivity and depth information, forward scattered electrons provide internal structure contrast, and transmission electrons provide high-resolution structural details, collectively achieving atomic resolution while compensating for spherical aberration 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 atomic size three-dimensional observation and identification of specimen structures, providing clear visualization of internal structures and material differences at the atomic level, overcoming the limitations of conventional techniques.
Implementation Method 1
a contrast referred to as 'Z-contrast ', which is proportional to the square of the atomic number Z of the specimen, can be obtained. This image is due to Rutherford scattering by the atomic nucleus
Implementation Method 2
Transmission electrons consist of electrons that have passed through the specimen and electrons that have lost energy slightly due to inelastic scattering
Implementation Method 3
an electron lens system having a small spherical aberration coefficient
Data Source
AI summary
A scanning transmission electron microscope according to the present invention includes an electron lens system having a small spherical aberration coefficient for enabling three-dimensional observation of a 0.1 nm atomic size structure. The scanning transmission electron microscope according to the present invention also includes an aperture capable of changing an illumination angle; an illumination electron lens system capable of changing the probe size of an electron beam probe and the illumination angle; a secondary electron detector (9); a transmission electron detector (13); a forward scattered electron beam detector (12); a focusing unit (16); an image processor for identifying image contrast; an image processor for computing image sharpness; a processor for three-dimensional reconstruction of an image; and a mixer (18) for mixing a secondary electron signal and a specimen forward scattered electron signal.