Electron Beam Deflection Compensation for Diffraction Overlap
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Solution Overview
Problem
Electron diffraction methods face challenges in analyzing small crystalline volumes due to strong interactions causing multiple scattering, leading to dynamical scattering effects and loss of phase information, which limits the applicability of kinematic theory and results in reduced structural information.
Innovation Solution
A method and device for measuring electron diffraction by deflecting the electron beam at an angle of incidence relative to the sample axis, with partial deflection compensation of diffracted and undiffracted beams, allowing detection of intensities as a function of incidence and scattering angles to reduce overlap and enhance structural information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the electron beam is deflected to hit the sample at large angles of incidence, then structural information can be enhanced, but diffraction reflections overlap and become unresolvable
Solution Approach 1:
The patent introduces a second deflection stage that operates in a different dimensional space from the incident beam deflection. While the incident beam is deflected in one dimension (to achieve large incidence angles), the transmitted beam is deflected in another dimension (to compensate for the shift). This dimensional separation allows both large incidence angles and resolved diffraction patterns to coexist.
Solution Approach 2:
The transmitted electron beam acts as an intermediary between the incident beam and the detector. By deflecting this intermediate beam, the system can compensate for the positional shifts caused by large incidence angle deflection, thereby maintaining reflection resolution while preserving structural information.
2Reliability
If very thin samples are used to reduce dynamical scattering effects, then kinematic theory becomes applicable, but the quantity of diffracted signal is reduced
Solution Approach 1:
The patent changes the parameter of incidence angle to large values, which alters the interaction geometry between electrons and the sample. This parameter change allows the use of thicker samples (increasing signal intensity) while still obtaining diffraction data that can be analyzed using modified kinematic approaches, as the large angle geometry reduces the path length through the sample.
3Loss of information
If convergent beam electron diffraction is used to solve the phase problem, then phase information can be obtained, but the angular range is limited by reflection overlap
Solution Approach 1:
The patent employs a two-stage deflection system where the second deflection stage operates in a compensatory dimension. This allows the system to access large incidence angles (expanding angular range) while maintaining reflection separation through the compensating deflection, thereby overcoming the angular range limitation of conventional CBED while preserving phase information capability.
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 enables the detection of unambiguous intensity data, reducing overlap of diffraction reflections and providing increased structural and phase information, even at large angles of incidence, beyond the limitations of conventional methods.
Implementation Method 1
an electron beam is directed onto a sample diffracted by the atomic structure of the sample. Depending on the structure of the sample, like a crystal lattice structure, diffraction leads to reflections at distinct scattering angles
Implementation Method 2
a beam deflection device for deflecting an electron beam incident on a sample
Implementation Method 3
an exit beam deflection compensation device for subjecting electron beams transmitted through the sample to a partial deflection compensation
Data Source
AI summary
The invention relates to a method and a device for measuring electron diffraction of a sample, including the steps of illuminating the sample with an incident electron beam which is deflected from a sample axis to hit the sample at an angle of incidence relative to the sample axis, at least partially subjecting the incident electron beam to diffraction by the sample, subjecting the diffracted and undiffracted electron beams transmitted through the sample to a partial deflection compensation, detecting the intensity of the diffracted and undiffracted electron beams transmitted through the sample in dependency on the angle of incidence and a scattering angle of the diffracted beam. The invention also relates to a computer program for controlling a transmission electron microscope for carrying out the inventive method.