Unveiling the Nottingham Inversion Instability during the thermo-field emission from refractory metal...

Area of Science:

• Physics
• Materials Science
• Electrical Engineering

Background:

• Electron emission from micro-protrusions is studied for over a century.
• Unstable behaviors and vacuum breakdown in these systems are not fully explained.
• Experimental studies of instabilities are difficult due to vacuum breakdown.

Purpose of the Study:

• To provide evidence on the mechanisms responsible for thermal instability during field emission from refractory metal micro-protrusions.
• To explain the origin of discontinuities or jumps in electron emitted current under high applied voltages.
• To introduce and define the Nottingham Inversion Instability.

Main Methods:

• Utilizing a model to study electron emission from refractory metals.
• Analyzing discontinuities in electron emitted current under high applied voltages.
• Correlating jumps in emission current with jumps in temperature.

Main Results:

• A jump in emission current and temperature occurs beyond a threshold electric field.
• These jumps are linked to a transient runaway of resistive heating after Nottingham flux inversion.
• Emitter geometry and high-temperature thermal conductivity are critical for initiating the runaway.

Conclusions:

• The Nottingham Inversion Instability explains thermal failures and breakdowns in field emitters.
• The phenomenon involves a heat reflux towards the emitting surface.
• Specific emitter geometry and thermal properties are required for this instability.