Dominant structural defects in amorphous silicon.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Amorphous silicon (a-Si) is a crucial material in electronics.
• Understanding its structural disorder is key to optimizing its properties.
• Coordination defects significantly influence a-Si's electronic and physical behavior.

Purpose of the Study:

• To investigate the nature of disorder in amorphous silicon.
• To analyze the spatial arrangement and energies of coordination defects.
• To understand the impact of atomic implantation and relaxation on these defects.

Main Methods:

• Numerical modeling of amorphous silicon structures.
• Analysis of spatial correlations between structural defects using a bond-sharing parameter.
• Calculation of partial bond angle distributions for local geometries.
• Molecular-dynamics simulations of high-energy atom implantation and relaxation.

Main Results:

• Pentacoordinated atoms are identified as the dominant coordination defects in a-Si.
• These pentacoordinated defects exhibit a clustering tendency, with 17% linked via three-membered rings.
• Tricoordinated sites are less frequent and tend to be spatially separated.
• Formation energies of structural defects were estimated.
• The effect of relaxation on defect environments after atomic implantation was simulated.

Conclusions:

• The clustering of pentacoordinated atoms is a primary source of disorder in amorphous silicon.
• The spatial distribution and local geometries of defects provide insights into the material's structure.
• Simulations reveal how energetic events and relaxation influence defect evolution in a-Si.