Electromigration and morphological changes in Ag nanostructures

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Electromigration (EM) is a critical phenomenon in nanoscale conductors.
• Understanding EM and thermal migration (TM) is essential for reliable nanodevice fabrication.
• Previous studies have explored EM in various metallic nanostructures.

Purpose of the Study:

• To investigate electromigration (EM) as a structuring tool for silver (Ag) nanowires.
• To analyze the interplay between EM and thermal migration (TM) in Ag nanostructures.
• To explore novel structure formation under high current densities.

Main Methods:

• Experimental investigation of Ag nanowires (300 nm width, 25 nm thickness) and patterned Ag structures.
• Utilized a four-tip scanning tunneling microscope (STM) combined with a scanning electron microscope (SEM).
• Performed simulations to estimate temperature, current density, and mass flux distributions.

Main Results:

• At critical current densities (10^8 A cm^-2), EM-induced voids formed at the cathode and hillocks at the anode.
• Electron wind force significantly dominated thermal diffusion at room temperature.
• A new wire-like structure formation was observed in notched and bow-tie Ag structures at high current densities, indicating simultaneous EM and TM influence.

Conclusions:

• Electromigration is an effective structuring tool for silver nanowires and nanostructures.
• The simultaneous action of EM and TM contributes to structure formation, particularly at higher current densities.
• Thermal migration has a minimal influence at low temperatures (100 K) compared to electromigration.