Tapered Sample Carrier for Electron Microscope X-Ray Shadowing
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Solution Overview
Problem
The existing lift-out grids for electron microscopes cause significant shadowing of X-rays due to their thickness, limiting the detection of emitted X-rays and resulting in longer processing times and reduced 3D reconstruction resolution, especially near the sample/grid interface, and alternative methods like using needles are cumbersome and prone to vibrations, affecting high-throughput and high-resolution imaging.
Innovation Solution
A sample carrier with a metal foil that has a reduced thickness at the mounting position, achieved through tapering, allowing for minimal shadowing of radiation and improved accessibility for electron detection, using materials like Mo, Ti, or Cu, and employing methods like laser ablation for fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick metal foil is used for the sample carrier, then the structural stability and vibration resistance are improved, but the shadowing of X-rays increases, reducing detection efficiency
Solution Approach 1:
The metal foil is designed with non-uniform thickness: thick (25-30 μm) in the bulk for structural stability, and thin (5-10 μm) at the mounting position for reduced X-ray shadowing. This local variation in thickness allows simultaneous achievement of mechanical stability and detection efficiency.
2Reliability
If a thick metal foil is used for the sample carrier, then the resilience to vibration and buckling is improved, but the processing time increases due to reduced X-ray detection
Solution Approach 1:
The differential thickness design enables the carrier to maintain vibration resistance through its thick bulk while reducing processing time by minimizing X-ray shadowing at the thin mounting position, allowing faster and more accurate elemental analysis.
3Strength
If a thick metal foil is used for the sample carrier, then the mechanical strength is improved, but the resolution of 3D reconstruction deteriorates near the sample/grid interface
Solution Approach 1:
The thin mounting position (5-10 μm) minimizes X-ray shadowing and improves 3D reconstruction resolution near the sample interface, while the thick bulk (25-30 μm) maintains mechanical strength for handling and mounting.
4Productivity
If the sample carrier thickness is reduced, then the X-ray shadowing is reduced, but the structural stability deteriorates
Solution Approach 1:
The carrier features localized thinning only at the mounting position where samples are attached, while the bulk remains thick to maintain structural stability. This allows reduced X-ray shadowing without compromising overall mechanical integrity.
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 reduces radiation shadowing, enhances detection efficiency, and improves throughput by minimizing sample loss and vibration, enabling higher resolution imaging and more accurate elemental analysis.
Implementation Method 1
In a Focused Ion Beam (FIB) machine... the sample is excavated from a work-piece
Implementation Method 2
In a TEM the lamella is irradiated with a beam of electrons with an energy of, for example, 300 keV, in response to which radiation is emitted. This radiation includes transmitted electrons, reflected electrons, secondary electrons, X-rays, etc.
Implementation Method 3
The X-rays can be used to form an image providing elemental information of the sample, based on the characteristic X-rays emitted from the lamella
Implementation Method 4
For optimum processing speed the detectors are placed to surround the sample so that X-rays emitted from as large an emittance solid angle as possible are detected
Data Source
Figure 1A~1B
Figure 2
AI summary
The invention relates to a sample carrier (10) for a transmission electron microscope. When using state of the art sample carriers, such as half-moon grids in combination with detectors detecting, for example, X-ray emitted at a large emittance angle, shadowing is a problem. Similar problems occur when performing tomography, in which the sample is rotated over a large angle. The invention provides a solution to shadowing by forming the parts (16) of the grid bordering the interface between sample and grid as tapering parts.