Decontamination in the Electron Probe Microanalysis with a Peltier-Cooled Cold Finger

Area of Science:

• Materials Science
• Analytical Chemistry
• Instrument Engineering

Background:

• Electron microprobes require cold fingers to minimize carbon contamination and improve vacuum.
• Traditional liquid nitrogen (LN2) cooling presents challenges such as vacuum degradation upon warming and handling difficulties.

Purpose of the Study:

• To develop and evaluate a Peltier thermoelectric cooling unit as an alternative to LN2 for electron microprobe cold fingers.
• To assess the impact of Peltier cooling on instrument performance, vacuum stability, and carbon contamination rates.

Main Methods:

• Construction of a prototype Peltier thermoelectric cooling unit.
• Testing the unit at different power inputs (15 W and 96 W) to achieve specific cold finger temperatures.
• Monitoring analytical stability, vacuum levels, and carbon contamination rates during operation.

Main Results:

• Achieved cold finger temperatures of -10°C and -27°C at 15 W and 96 W, respectively.
• Demonstrated no adverse effect on the electron microprobe's analytical stability.
• Observed efficient heat conduction from the external Peltier unit to the internal cold finger.
• Prevented vacuum degradation typically seen when warming from LN2 temperatures.
• Reduced carbon contamination rates, comparable to LN2-cooled devices at -27°C.

Conclusions:

• Peltier thermoelectric cooling is a viable alternative for electron microprobe cold fingers.
• It offers advantages over LN2 cooling, including simplified operation and avoidance of vacuum issues.
• The system effectively reduces carbon contamination, enhancing analytical performance.