Diffusion of Rhodium Atoms in Neutron-Irradiated Silicon and Their Effect on Structural and Phase Changes

Abstract High-purity silicon is one of the most important materials used in nanoelectronics and microelectronics because its structural and electrical properties are highly sensitive to impurities and crystal defects. In this study, the diffusion behavior of rhodium (Rh) atoms in neutron-irradiated silicon and the resulting structural-phase changes were investigated by X-ray diffraction analysis. Rh atoms were introduced into silicon by gas-phase diffusion at 1250°C for 5 h, followed by two different cooling regimes: slow cooling and rapid cooling. The diffraction results showed that all samples preserved the (111) crystallographic orientation, while significant changes were observed in lattice parameters, peak intensity, and secondary phase formation depending on the treatment conditions. Heat treatment increased the intensity of the (111)Si reflection and slightly expanded the lattice constant, indicating relaxation of the crystal lattice and reduction of microstresses. After Rh diffusion with slow cooling, the lattice constant decreased, which suggests lattice densification caused by the incorporation of Rh atoms. In contrast, rapid cooling led to lattice expansion and promoted the formation of a new rhodium silicide (SiRh) phase. Additional reflections corresponding to SiOx, SiO2, and SiB6 phases were also identified, confirming the formation of nanoscale secondary structures. Analysis of the forbidden reflection intensity ratio I(222)/I(111) showed that rapid cooling significantly reduced microstresses and defects in the silicon lattice. These results demonstrate that Rh diffusion combined with controlled cooling is an effective way to modify the structural state of neutron-irradiated silicon.

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