Electron backscattering coefficient, material contrast and response function of BSE- detectors in scanning electron...

Area of Science:

• Materials Science
• Physics
• Electron Microscopy

Background:

• Accurate characterization of electron backscattering is crucial for quantitative analysis in scanning electron microscopy (SEM).
• Existing models for electron backscattering coefficients (η) and detector response functions (F) have limitations in precision and energy range.
• Understanding the dependence of backscattered electron (BSE) signals on material properties and SEM parameters is essential for image formation.

Purpose of the Study:

• To establish precise empirical expressions for the electron backscattering coefficient (η), mean backscattered energy coefficient (ε), and response function (F) of BSE detectors.
• To investigate the dependence of the BSE signal (I_S) on the atomic number (Z) of the target material and primary electron energy (E_B).
• To analyze the influence of the response function (F) on BSE signal formation and image contrast in SEM.

Main Methods:

• Development of empirical expressions for η, ε, and F based on atomic number (Z) and primary electron energy (E_B).
• Validation of expressions across a wide energy range (1-30 keV) for bulk specimens.
• Comparison of characteristics obtained with commercial semiconductor/scintillation BSE detectors against multichannel plate (MCP) detectors.

Main Results:

• Established new empirical expressions providing more accurate η data than previous studies over the 1-30 keV energy range.
• Described the dependence of the BSE signal (I_S) on target material atomic number (Z) and SEM accelerating voltage (E_B).
• Quantified the influence of the response function (F) on BSE signal formation and image contrast, considering Z-differences and E_B.

Conclusions:

• The derived empirical expressions offer improved accuracy for BSE signal quantification in SEM.
• The study provides a better understanding of image contrast formation influenced by material composition and SEM operating parameters.
• The findings are applicable to standard SEM BSE detectors and offer a basis for further detector characterization.