Magnetizable Phase Plate for TEM Imaging
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Solution Overview
Problem
Conventional phase plates for charged particle beam systems, such as transmission electron microscopes, face challenges in enhancing phase contrast for weak phase objects, including energy dependency, contamination, beam-induced charge-up, and difficulty in controlling phase shift, particularly at low spatial frequencies, which hinders effective imaging of biological samples.
Innovation Solution
A phase plate design featuring a magnetizable elongate member with a narrow cross-section that extends partially across a through-hole, introducing a spiral-like phase shift to charge carriers, allowing a wider range of spatial frequency components to pass through while reducing contamination and shadowing artefacts, and is fabricated using materials like nickel, cobalt, and iron.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional phase plate (film-based or electrostatic lens) is used to enhance phase contrast, then phase contrast at low spatial frequencies is improved, but the device is prone to contamination, charge-up, and energy dependency
Solution Approach 1:
The patent replaces the mechanical film-based phase plate or electrostatic lens system with a magnetic field-based phase plate. The magnetic field is generated by a magnetizable elongate member that creates a spiral-like phase shift in the electron wave without physical contact with the beam, eliminating contamination and charge-up issues while maintaining phase contrast enhancement
Solution Approach 2:
The patent changes the fundamental parameter from using physical thickness or electrostatic voltage to using magnetic flux density. The magnetic field strength and distribution are controlled by the magnetizable material properties and geometry, providing energy-independent phase shift control that avoids the limitations of conventional approaches
2Illumination intensity
If a film-based phase plate is used, then phase contrast is enhanced, but it is difficult to control accurately the thickness and the phase shift
Solution Approach 1:
The patent substitutes the mechanical thickness-based phase shift mechanism with a magnetic field-based mechanism. Instead of controlling film thickness to achieve the desired phase shift, the invention uses magnetizable materials with specific remanent magnetization values that directly determine the phase shift, eliminating thickness control difficulties
Solution Approach 2:
The patent transitions from controlling geometric parameter (film thickness) to controlling magnetic parameter (remanent magnetization). The phase shift is determined by the magnetic flux density which can be precisely controlled through material selection and magnetization processes, achieving accurate phase shift control without thickness measurement and control issues
3Object-affected harmful factors
If the elongate member is made narrower to reduce contamination, then fewer spatial frequency components are blocked, but the phase shift control becomes more challenging
Solution Approach 1:
The patent uses composite material structure combining a narrow magnetizable elongate member with a ferromagnetic material having specific magnetic properties. The composite approach allows the narrow geometry to minimize contamination and spatial frequency blocking while the ferromagnetic material provides sufficient magnetic flux for effective phase shift control
Solution Approach 2:
The patent compensates for the reduced cross-sectional area by changing the magnetic parameter - using materials with high remanent magnetization values. This allows a narrow elongate member to generate adequate magnetic flux for phase shift control while maintaining the contamination-reducing narrow geometry
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 design enhances phase contrast at low spatial frequencies, reduces contamination, and minimizes shadowing artefacts, enabling clearer imaging of biological samples with improved contrast and reduced electron dose, thus overcoming the limitations of existing phase plates.
Implementation Method 1
an elongate member which is magnetisable in a direction along its length and which extends partially across the through-hole
Implementation Method 2
introducing a spiral-like phase shift to charge carriers
Data Source
AI summary
A phase plate for a charged particle beam system, such as a transmission electron microscope (TEM), is described. The phase plate comprises a support having a through-hole and an elongate member which is magnetisable in a direction along its length and which extends partially across the through-hole and which is narrower than the through-hole.