Overview of S(T)EM electron detectors with garnet scintillators: Some potentials and limits

Area of Science:

• Materials Science
• Electron Microscopy
• Optical Engineering

Background:

• Scintillation electron detectors are crucial for Scanning Electron and/or Scanning Transmission Electron Microscopes (S(T)EM).
• Garnet scintillators offer potential for enhanced detector performance.
• Optimizing light collection and scintillator properties is key for high-resolution imaging.

Purpose of the Study:

• To present a complete configuration and design of a scintillation electron detector for S(T)EM utilizing garnet scintillators.
• To analyze all processes related to scintillator and light guide performance.
• To optimize detector design for improved low-energy electron detection and imaging contrast.

Main Methods:

• Analysis of excitation electron trajectories and absorbed energy distributions.
• Evaluation of scintillator efficiencies, kinetics, and optical properties, including anti-charging coatings and substrates.
• Computer-optimized design using the SCIUNI application for light guide systems.

Main Results:

• Low-energy detection (<1 keV) requires a 3 nm scandium conductive coating for electron penetration.
• LuGdGaAG:Ce garnet films provide short rise/decay times and low afterglow, enhancing modulation transfer function to 0.6 lp/pixel.
• Optimized light guides achieve over 20% efficiency, significantly outperforming non-optimized systems (1%).

Conclusions:

• Thin film scintillators minimize signal self-absorption, improving detection.
• Careful selection of materials and optimized light guide design are critical for high-performance S(T)EM detectors.
• The developed detector configuration offers superior contrast transfer and efficiency, particularly at low electron energies.