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Deterministic Role of Collision Cascade Density in Radiation Defect Dynamics in Si
J B Wallace1,2, L B Bayu Aji1, L Shao2
1Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Physical Review Letters
|June 9, 2018
Summary
Dynamic annealing of radiation damage in silicon is influenced by irradiation conditions. A pulsed ion beam method reveals cascade density as a key parameter controlling defect dynamics and annealing rates across different temperatures.
Area of Science:
- Materials Science
- Solid State Physics
- Nuclear Engineering
Background:
- Stable radiation damage in solids forms through complex dynamic annealing (DA) processes involving point defect migration and interaction.
- The precise influence of irradiation conditions on DA remains poorly understood, particularly in silicon (Si).
- Understanding defect dynamics is crucial for predicting material behavior under irradiation.
Purpose of the Study:
- To investigate defect interaction dynamics in silicon under varying irradiation conditions using a pulsed ion beam method.
- To determine the key parameters governing dynamic annealing (DA) of radiation damage in silicon.
- To establish a predictive model for radiation defect dynamics in silicon based on irradiation parameters.
Main Methods:
- Bombardment of silicon with ions ranging from Neon (Ne) to Xenon (Xe) to create collision cascades of varying densities.
- Utilized a pulsed ion beam technique to study defect interaction dynamics.
- Analyzed dynamic annealing (DA) rates across a temperature range of approximately -30°C to 210°C.
Main Results:
- The complexity of irradiation condition effects on defect dynamics can be simplified to the average cascade density, considering fractal cascade structures.
- DA rates in silicon exhibit two distinct Arrhenius regions with different dominant DA mechanisms, intersecting at a critical temperature dependent on cascade density.
- The low-temperature DA regime shows a cascade density-independent activation energy (~0.1 eV), while the high-temperature regime reveals an increased activation energy above ~0.04 at.% cascade density.
Conclusions:
- Collision cascade density is a critical parameter that governs dynamic annealing processes in silicon.
- The findings provide a framework to predict radiation defect dynamics in silicon based on irradiation conditions.
- This research advances the understanding of radiation damage formation and mitigation strategies in silicon-based materials.
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