We demonstrate the broadband visible luminescence from bulk crystalline silicon and silicon nanoparticles sized 100- 30 nm under near-infrared excitation. We show that the luminescence spectrum has two distinct peaks. The first being centered at 550 nm while the second appears close to the wavelength of the second harmonic of the excitation light. The appearance of the second peak is a signature of the highly athermal electron distribution never observed previously. The luminescence intensity and spectral shape strongly depend on the doping type and concentration. Despite being nonresonant, silicon nanoparticles enhance luminescence intensity when placed atop the silicon wafer. The observed phenomenon can be used for wafer inspection and defect detection, as well as for the creation of novel nanosources of light.
Detection of a single nanoparticle on a bare silicon wafer has been a challenge in the semiconductor industry for decades. Currently, the most successful and widely used technique is dark-field microscopy. However, it is not capable of detecting single sub-10 nm particles owing to a low signal-to-noise ratio (SNR). As a new approach, we suggest using the second harmonic generation (SHG) to detect a single nanoparticle. The second harmonic generation in centrosymmetric materials, like silicon, is forbidden except for a thin and additionally increase local field factors, allowing for their persistent detection. Choosing the proper surface and increasing SNR. We demonstrate the feasibility of the nonlinear dark-field microscopy concept by detecting an isolated 80-nm silicon nanoparticle on the silicon wafer.