Zone Axis Alignment Using Laue Circle Segmentation
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Solution Overview
Problem
Existing methods for aligning the zone axis of a crystalline sample with a charged particle beam face challenges when diffraction spots are mixed due to sample curvature or irradiation with a convergent beam, leading to inaccurate nanoscale feature measurement.
Innovation Solution
A method involving directing a charged particle beam towards a sample, acquiring a diffraction pattern, segmenting the Laue circle using a trained network, and tilting the sample based on the determined zone axis tilt to align the zone axis automatically, even with bendy samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If diffraction pattern is acquired with parallel beam, then zone axis alignment can be performed, but diffraction spots become mixed and difficult to identify when sample is curved or bendy
Solution Approach 1:
The patent changes the beam convergence parameter from parallel (zero convergence) to convergent beam geometry. This parameter change transforms the diffraction pattern characteristics, allowing the use of disk-shaped diffraction features instead of spot-based features for alignment, thereby resolving the identification difficulty with curved samples
Solution Approach 2:
The patent replaces the traditional mechanical/visual identification method of diffraction spots with an automated image processing and pattern recognition system. This substitution enables automatic identification and alignment without manual intervention, overcoming the difficulty of identifying mixed diffraction spots
2Extent of automation
If convergent beam is used for irradiation, then diffraction spots become disks that can be automatically identified, but diffraction spots become elongated and overlapped with each other and direct beam
Solution Approach 1:
The patent introduces an intermediary processing layer between the diffraction pattern acquisition and zone axis determination. This intermediary layer applies image processing algorithms to deconvolute and separate the overlapping diffraction disks, recovering the underlying crystallographic information despite the overlaps
Solution Approach 2:
The patent creates a processed representation or copy of the diffraction pattern through image processing algorithms. This processed copy separates and identifies individual diffraction features even when they appear overlapped in the original pattern, enabling reliable automatic alignment
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 accurate alignment of the zone axis with the incident beam, allowing for high-resolution imaging of curved or bendy samples by determining the zone axis tilt using a trained network, ensuring precise segmentation and alignment.
Implementation Method 1
When the parallel charged particle beam passes through a thin crystalline sample, the charged particles interfere with each other and form a diffraction pattern on the back focal plane of an objective lens positioned below the sample
Implementation Method 2
the charged particles interfere with each other and form a diffraction pattern
Data Source
AI summary
Automatic alignment of the zone axis of a sample and a charged particle beam is achieved based on a diffraction pattern of the sample. An area corresponding to the Laue circle is segmented using a trained network. The sample is aligned with the charged particle beam by tilting the sample with a zone axis tilt determined based on the segmented area.