Structure and low-temperature thermal relaxation of ion-implanted germanium

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Ion implantation is a key technique for modifying semiconductor properties.
• Understanding implantation-induced damage in germanium (Ge) is crucial for device fabrication.
• Extended X-ray absorption fine structure spectroscopy (EXAFS) provides atomic-level structural insights.

Purpose of the Study:

• To investigate the structural evolution of germanium during ion implantation-induced amorphization.
• To characterize the amorphous phase and its response to thermal annealing.
• To elucidate the role of coordination defects in the amorphous structure.

Main Methods:

• High-resolution extended X-ray absorption fine structure (EXAFS) spectroscopy was employed.
• EXAFS data were analyzed using the Cumulant Method.
• Structural changes were monitored as a function of ion dose and annealing temperature.

Main Results:

• A progressive increase in bond length without asymmetry was observed during the crystalline-to-amorphous transformation.
• Beyond the amorphization threshold, bond length and asymmetry increased with ion dose.
• The amorphous phase exhibited dose-dependent and asymmetric interatomic distance distribution (RDF), attributed to 3- and 5-fold coordinated atoms.
• Low-temperature annealing induced structural relaxation, reducing RDF centroid, asymmetry, and width, correlating with a decrease in non-4-fold coordinated atoms.

Conclusions:

• The study provides detailed insights into the structural transformations of germanium under ion irradiation.
• The formation and relaxation of coordination defects significantly influence the amorphous structure of germanium.
• Comparison with other EXAFS studies suggests sample preparation and relaxation state affect reported bond lengths in amorphous germanium.