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Signal components in the environmental scanning electron microscope.
1Polymers and Colloids Group, Cavendish Laboratory, Department of Physics, Madingley Road, University of Cambridge, Cambridge CB3 0HE, U.K.
Journal of Microscopy
|December 14, 1999
Summary
Environmental scanning electron microscopy (ESEM) signals contain both useful and unwanted components. This study separates secondary and backscattered electron signals, revealing how gas pressure and chemistry affect ESEM imaging quality.
Area of Science:
- Surface Science
- Materials Science
- Electron Microscopy
Background:
- Environmental scanning electron microscopy (ESEM) utilizes gas amplification to detect electron signals.
- The detected signal in ESEM is a composite of secondary electrons (SE) and backscattered electrons (BSE), along with gas ionization background.
- Distinguishing between SE and BSE contributions is crucial for accurate material characterization in ESEM.
Purpose of the Study:
- To differentiate and quantify the contributions of secondary and backscattered electrons in gas-amplified ESEM signals.
- To investigate the influence of gas pressure and gas chemistry on the signal composition and amplification efficiency.
Main Methods:
- Utilized two sets of sample pairs with specifically chosen secondary and backscatter coefficients.
- Examined signal variations across different pressures of the amplifying gas.
- Analyzed the impact of varying gas chemistries on electron signal amplification.
Main Results:
- Demonstrated that both desired (SE) and spurious (BSE, gas ionization) signal components are present in gas-amplified ESEM.
- Showed that backscattered electron contributions and gas ionization background increase significantly with higher gas pressure.
- Confirmed that the relative amplification efficiencies of different electron signals are dependent on the amplifying gas's chemical properties.
Conclusions:
- Effective separation of SE and BSE signals in ESEM requires careful consideration of gas pressure and chemistry.
- Optimizing gas parameters is essential for minimizing spurious signals and enhancing the quality of ESEM imaging.
- Understanding gas-electron interactions provides a pathway for improved quantitative analysis in ESEM.
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