Long-term stability of Cu surface nanotips

Area of Science:

• Materials Science
• Surface Physics
• Computational Modeling

Background:

• Sharp nanoscale tips on metal electrodes concentrate electric fields, leading to electron emission and atom evaporation.
• These phenomena are implicated in electric discharges observed near metal surfaces, even in ultra-high vacuum.
• Understanding the stability of these nanotips is critical for high-voltage electronics applications.

Purpose of the Study:

• To investigate the stability and lifetime of copper (Cu) surface nanotips at various temperatures using computer simulations.
• To develop and validate a surface kinetic Monte Carlo (KMC) model for simulating atomic surface processes.

Main Methods:

• Developed a surface kinetic Monte Carlo (KMC) model incorporating precalculated energy barriers for atomic jump processes.
• Simulated surface diffusion on copper nanotips at different temperatures.
• Validated the KMC model against molecular dynamics (MD) simulations for accuracy and computational efficiency.

Main Results:

• Tall, high-aspect-ratio nanotips exhibit considerable stability at room temperature.
• Nanotip stability is highly temperature-dependent; 13 nm nanotips flatten significantly within 100 ns near the melting point, but show minimal change after 10^5 s at room temperature.
• Nanotips oriented along the [110] crystallographic direction are substantially more stable than those along [100] or [111] directions.

Conclusions:

• The KMC model effectively simulates atomic surface processes and offers a computationally efficient alternative to MD simulations.
• Copper nanotips are stable at room temperature but their lifetime is drastically reduced at elevated temperatures.
• Crystallographic orientation significantly influences nanotip stability, with [110] offering superior robustness for high-voltage applications.