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Figure of merit for environmental SEM and its implications
1ESEM Research Laboratory, 28 Wallis Parade, North Bondi, Australia. Professorgerry@danilatos.com
Journal of Microscopy
|September 8, 2011
Summary
A new figure of merit for environmental scanning electron microscopes was calculated across all pressures. A pressure-limiting aperture serves as an optimal reference system for differential pumping in electron microscopy.
Area of Science:
- Materials Science
- Physics
- Analytical Chemistry
Background:
- Environmental scanning electron microscopy (ESEM) and low-vacuum SEM (LVSEM) enable imaging under higher pressures.
- Characterizing performance across the full operational pressure range is crucial for ESEM and LVSEM.
- A figure of merit is needed to quantify performance in these instruments.
Purpose of the Study:
- To compute a recently introduced figure of merit for ESEM/LVSEM across the full operational pressure range.
- To consolidate the theory of this figure of merit.
- To investigate the utility of a pressure-limiting aperture as a reference system.
Main Methods:
- Direct Simulation Monte Carlo (DSMC) method was employed for computation.
- Theoretical analysis was performed to consolidate the figure of merit's theory.
- Simulations were conducted for a commercial ESEM instrument.
Main Results:
- The figure of merit was computed for the full operational pressure range of a commercial instrument.
- The direct simulation Monte Carlo method proved effective in lieu of experimental measurements.
- A thin pressure-limiting aperture was identified as an optimal reference system for differential pumping.
Conclusions:
- The study validates the figure of merit and its theoretical underpinnings.
- A pressure-limiting aperture is a viable and optimal reference for differential pumping systems in electron microscopy.
- Results provide a foundation for improving commercial ESEM/LVSEM instruments and future research.
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