Giant Barkas effect observed for light ions channeling in Si

Area of Science:

• Physics
• Materials Science
• Nuclear Instruments and Methods

Background:

• Electronic energy loss is crucial for understanding ion-matter interactions.
• The Barkas effect describes an enhancement in energy loss related to projectile charge.
• Previous studies have explored energy loss but detailed Barkas effect analysis in silicon channeling is ongoing.

Purpose of the Study:

• To measure and analyze the electronic energy loss of helium and lithium ions in silicon.
• To isolate and quantify the Barkas effect during ion channeling.
• To compare experimental Barkas effect contributions with theoretical predictions, specifically the Lindhard model.

Main Methods:

• Channeling of (4)He and (7)Li ions along main axial directions in silicon.
• Measurements conducted at intermediate to high projectile energies.
• Separation of the Barkas effect from other energy loss contributions.

Main Results:

• Clear observation and separation of the Barkas effect for (4)He and (7)Li ions in silicon.
• The Barkas effect was found to enhance energy loss significantly, reaching approximately 50% for (7)Li ions along the Si [110] direction.
• Experimental Barkas contribution from the valence-electron gas showed good agreement with the Lindhard model.

Conclusions:

• The Barkas effect is a dominant factor in electronic energy loss for channeling ions under specific conditions.
• Experimental data validates the predictions of the Lindhard model regarding the Barkas effect in silicon.
• This study provides valuable data for ion channeling and energy loss phenomena in semiconductor materials.