Gold-Induced grain growth suppression and metallic conductivity in nanocrystalline silicon via pulsed laser annealing

Abstract

Pulsed laser annealing (PLA) constitutes a powerful tool for nonequilibrium engineering of thin-film semiconductor properties. In this work, we investigate the impact of deep gold doping on the structural evolution and electronic properties of amorphous silicon films (α-Si:Au) subjected to nanosecond-scale PLA. Gold is shown to play a dual physical role: first, it effectively suppresses crystallite coalescence, limiting crystallite size to 2.3–2.8 nm and preserving a heterophase structure with a high crystalline fraction (up to 78%), as quantitatively corroborated by Raman spectroscopy and the phonon confinement model; second, at concentrations of approximately ~ 5 · 10²⁰ cm^-3, gold promotes the formation of a degenerate electron gas, manifesting as metallic-like behavior in the mid-infrared spectral range (2.5–5.0 µm). Key transport parameters—namely, carrier mobility \(\left\langle \upmu \right\rangle =76\pm 8\,\mathrm{cm}^{2}/\left(\mathrm{V}\cdot \mathrm{s}\right)\left\langle \upmu \right\rangle =76\pm 8\,\mathrm{cm}^{2}/\left(\mathrm{V}\cdot \mathrm{s}\right)\) and resistivity ⟨ρ⟩ = (1.7 ± 0.2) · 10⁻⁴ Ω · cm—were extracted from reflectance spectra using the Drude model. Despite the high density of defects and amorphous interlayers, the system achieves metallic conductivity owing to the elevated concentration of free carriers. These findings demonstrate the feasibility of synergistically tailoring both the nanostructure and electronic properties of silicon through the combined strategy of deep doping and ultrafast thermal processing, thereby opening new avenues for the development of functional silicon-based nanocomposites in optoelectronics and nanoelectronics.