Analysis of silicon nanocrystals in silicon-rich SiO<sub>2</sub> synthesized by CO<sub>2</sub> laser annealing

Chun-Jung Lin; Gong-Ru Lin; Yu-Lun Chueh; Li-Jen Chou

doi:10.1117/12.636158

2 December 2005 Analysis of silicon nanocrystals in silicon-rich SiO₂ synthesized by CO₂ laser annealing

Chun-Jung Lin, Gong-Ru Lin, Yu-Lun Chueh, Li-Jen Chou

Proceedings Volume 6020, Optoelectronic Materials and Devices for Optical Communications; 602020 (2005) https://doi.org/10.1117/12.636158
Event: Asia-Pacific Optical Communications, 2005, Shanghai, China

Abstract

The localized synthesis of 4.2-5.6 nm-Si nanocrystals (nc-Si) in Si-rich SiO₂ (SRSO) by CO₂laser annealing at laser intensity of below ablation-threshold (6 kW/cm²) is demonstrated. Since the SRSO exhibits a high absorption coefficient of up to 0.102 cm^-1 at wavelength of 10.6 μm, a direct-writing CO₂ laser annealing system with focusing spot size of 0.2 mm² is used to locally anneal the SRSO and precipitate the nc-Si. A thermophysical model reveals that the surface temperature of SRSO ranging from 130^oC to 3350^oC is achieved by varying the laser power densities from 1.5 to 13.5 kW/cm². The CO₂ laser-ablation-threshold power density is about 6 kW/cm², corresponding to the optimized annealing temperature 1285^oC at the ablation threshold. The CO₂laser annealing is capable of the precise control on power density and spot size, which benefits from the in-situ and localized annealing temperature control of SRSO film, and also prevents from the eternal damage of the other electronic devices nearby the annealing site. The nc-Si dependent photoluminescence (PL) were observed at 806 nm or longer, whereas the laser-ablation damaged SRSO film exhibits significant blue PL at 410 nm due to the oxygen-related structural defects. The refractive index of the lasertreated SRSO film is increasing from 1.57 to 2.31 as the laser intensity increases from 1.5 to 6.0 kW/cm² which is mainly attributed to the increasing density of nc-Si embedded in SRSO. High resolution transmission electron microscopy (HRTEM) analysis reveals that the average size of nc-Si embedded in SRSO film is about 5.3 nm, which correlates well with the theoretical prediction of a corresponding PL at 806 nm. The HRTEM estimated square density of the nc-Si in SRSO film under the laser intensity of 6 kW/cm² is about 10¹⁸ cm^-3.

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Chun-Jung Lin, Gong-Ru Lin, Yu-Lun Chueh, and Li-Jen Chou "Analysis of silicon nanocrystals in silicon-rich SiO₂ synthesized by CO₂ laser annealing", Proc. SPIE 6020, Optoelectronic Materials and Devices for Optical Communications, 602020 (2 December 2005); https://doi.org/10.1117/12.636158

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