Quantum-sized silicon for enhanced photoluminescence and optical nonlinearity

Abstract

Full-scale size control of intrinsic nanomaterials is highly desired but far from satisfactory. Herein, we report a robust strategy capable of mechanically tailoring bulk silicon (Si) into Si nanoparticles (SiNPs). The as-produced SiNPs are single crystalline with intrinsic characteristics. The combination of silica-assisted ball-milling and sonication-assisted solvent treatment, as well as cascade centrifugation, enables narrow-band size control over wide ranges (133–11 nm). The production process is highly reproducible with an overall yield up to 78 wt%. Strong size effects are observed in the spectroscopy, photoluminescence (PL), and nonlinear saturation absorption (NSA) of the SiNPs. Notably, the Si quantum dots (SiQDs) with an average size of 11 nm demonstrate significantly enhanced PL and NSA performances. An absolute modulation depth of 35.9% and saturation intensity of 1.53 MW cm⁻² (153 nJ cm⁻²) are derived for the SiQDs. Such a high nonlinear response and low excitation power would prompt the practical application of quantum-sized Si in mode-locked lasers and related fields.