Radiation enhanced silicon self-diffusion and the silicon vacancy at high temperatures

Area of Science:

• Materials Science
• Solid-State Physics
• Nuclear Engineering

Background:

• Self-diffusion is crucial for understanding material behavior under various conditions.
• Radiation can significantly alter diffusion mechanisms in solids.
• Silicon isotope heterostructures provide a unique system for studying diffusion.

Purpose of the Study:

• To investigate proton radiation enhanced self-diffusion (RESD) in Si-isotope heterostructures.
• To determine the migration enthalpy of vacancies at high temperatures under irradiation.
• To elucidate the temperature-dependent diffusion behavior of vacancies.

Main Methods:

• Performing self-diffusion experiments under proton irradiation.
• Utilizing Si-isotope heterostructures.
• Conducting experiments at temperatures ranging from 780°C to 872°C.
• Applying detailed modeling of RESD data.

Main Results:

• Vacancies exhibit a migration enthalpy of H(m)(V)=(1.8±0.5) eV at high temperatures during RESD.
• This high-temperature migration enthalpy is significantly slower than expected based on low-temperature diffusion (H(m)(V)<0.5 eV).
• Direct evidence for temperature-dependent vacancy diffusion was obtained.

Conclusions:

• The observed slower vacancy diffusion at high temperatures is attributed to their microscopic configuration.
• Increasing temperature leads to an increase in the entropy and enthalpy of vacancy migration.
• This finding provides new insights into diffusion mechanisms under irradiation.