Fabrication of Sintered Si Nano-polycrystalline with Reduced Si Nanoparticles and Properties of Photoluminescence in Visible Regime for Sintered Si Nano-polycrystalline by Violet Light Excitation

Abstract

Si oxide powder is reduced by highly repetitive pulse laser ablation in liquid, and Si nanoparticles are produced efficiently with a low cost in a short time. A Si nanopaste with highly doped Si nanoparticles was sintered by using a hot plate. We succeeded in fabricating a sintered Si nano-polycrystalline for the first time. The structure and components of the fabricated sintered Si nano-polycrystalline were investigated by SEM and EDX analysis. Furthermore, the reduced Si nanoparticles and the sintered Si nano-polycrystalline were excited by violet light and stable photoluminescence (PL), which were observed in the visible regime. The peak wavelengths of the PL were 550 nm and 560 nm. Particularly, the intensity of the observed PL of the sintered Si nano-polycrystalline was five times higher than that of the reduced Si nanoparticles powder. This result is attributed to the PL being amplified inside the sintered Si nano polycrystalline. These experiments show that because the mean diameters of the Si nanocrystals in the reduced Si nanoparticles were below 2 nm, the structure of the Si nanocrystals changed to a direct-transition type; the bandgap energy of the Si nanocrystals changed from 1.1 eV to 2.25 eV, and PL in the visible regime was generated. Moreover, the possibility of Si photonics is discussed. The sintered Si nano-polycrystalline will be applicable to light waveguides, optical switches using a free carrier effect, and light amplifiers