TEM Cathodoluminescence Fiber Optic Collection System
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Solution Overview
Problem
Current transmission electron microscopy (TEM) systems face challenges in simultaneously and accurately measuring cathodoluminescence (CL) light emitted from both the upstream and downstream surfaces of thin samples due to tight space constraints and inefficiencies in light collection, which affects the analysis of spectral information and Cherenkov radiation.
Innovation Solution
The implementation of separate fiber optics for CL light collection from collection mirrors above and below the sample, coupled with coupling optics to correct numerical aperture mismatches, allows for simultaneous and separate spectral measurement of CL light, enabling the creation of distinct spectra and calculation of difference spectra to isolate sample properties and radiation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate fiber optics are used for CL light collection from upstream and downstream surfaces, then measurement precision of spectral information is improved, but device complexity increases
Solution Approach 1:
The light collection system is segmented into separate fiber optics for upstream and downstream surfaces, allowing independent collection and measurement of CL light from each surface without signal mixing, thereby improving measurement precision
Solution Approach 2:
Coupling optics are introduced as intermediary components to bridge the collection mirrors and fiber optics, correcting numerical aperture mismatches and optimizing light transfer efficiency while maintaining the segmented collection architecture
2Productivity
If collection mirrors are placed close to the sample in TEM, then light collection efficiency is improved, but space constraints worsen
Solution Approach 1:
The collection mirrors are nested within the TEM sample holder structure, with upstream and downstream mirrors positioned on opposite sides of the sample within the limited space, maximizing light collection efficiency without exceeding volume constraints
Solution Approach 2:
The system transitions from single-sided to dual-sided light collection by placing mirrors in three-dimensional space above and below the sample, effectively utilizing the vertical dimension to improve collection efficiency within constrained lateral space
3Loss of time
If combined light from both surfaces is measured, then measurement speed is improved, but measurement precision of surface-specific properties deteriorates
Solution Approach 1:
The measurement system segments the CL light signals from upstream and downstream surfaces into separate detection channels using dedicated fiber optics, enabling simultaneous measurement while preserving surface-specific spectral information for precise analysis
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 precise and simultaneous analysis of CL light from both surfaces, improving the characterization of sample properties and dielectric responses by preventing signal mixing and allowing real-time calculation of difference spectra, thereby enhancing the understanding of sample properties and radiation interactions.
Implementation Method 1
When a high-energy charged particle such as an electron or ion beam strikes a sample, photons can be emitted depending on the sample material. This phenomenon is known as cathodoluminescence (CL).
Implementation Method 2
The higher energy electrons used in TEMs are more prone to generating braking radiation, also known as Cherenkov radiation, due to the electrons travelling through the sample faster than the phase velocity of light in the sample medium.
Implementation Method 3
A common way to collect photons emitted via CL is via a collection-mirror located on axis with the electron beam (e-beam) and either above (as is typical with bulk samples examined in the scanning electron microscope (SEM)), below the sample or both above and below the sample (as is typical for transmission electron microscopes (TEM)).
Data Source
AI summary
Apparatuses for collection of upstream and downstream transmission electron microscopy (TEM) cathodoluminescence (CL) emitted from a sample exposed to an electron beam are described. A first fiber optic cable carries first CL light emitted from a first TEM sample surface, into a spectrograph. A second fiber optic cable carries second CL light emitted from a second TEM sample surface into the spectrograph. The first and second fiber optic cables are positioned such that the spectrograph produces a first light spectrum for the first fiber optic cable and a separate light spectrum for the second fiber optic cable. The described embodiments allow collection of TEM CL data in a manner that allows analyzing upstream and downstream TEM CL signals separately and simultaneously with an imaging spectrograph.