Self-Diffusion in Amorphous Silicon by Local Bond Rearrangements

Area of Science:

• Materials Science
• Solid-State Physics
• Semiconductor Research

Background:

• Amorphous silicon (a-Si) is a crucial material in semiconductor technology.
• Understanding diffusion mechanisms in a-Si is vital for device fabrication and reliability.
• Previous studies suggested extended defects mediate self-diffusion in a-Si.

Purpose of the Study:

• To investigate self-diffusion in amorphous silicon (a-Si) at elevated temperatures.
• To determine the mechanism governing self-diffusion in a-Si.
• To compare the activation enthalpy of self-diffusion with other related processes.

Main Methods:

• Preparation of amorphous silicon using Si ion implantation of isotope multilayers.
• Annealing experiments at temperatures ranging from 460 to 600°C.
• Analysis of Si isotope profiles using secondary ion mass spectrometry (SIMS).

Main Results:

• Structural relaxation did not cause significant intermixing.
• Significant self-diffusion was observed before recrystallization.
• The temperature dependence of self-diffusion followed an Arrhenius law with Q=(2.70±0.11) eV.

Conclusions:

• Self-diffusion in amorphous silicon is primarily mediated by local bond rearrangements.
• The activation enthalpy for self-diffusion matches that of hydrogen diffusion and bond defect migration.
• Findings challenge previous hypotheses attributing self-diffusion to extended defect migration.