Fabrication of nanocrystalline silicon gratings embedded within a silicon nitride matrix by femtosecond laser-induced crystallization

Nanocrystalline silicon gratings were fabricated by applying both femtosecond-laser-interference crystallization and post thermal annealing to amorphous silicon (a-Si) nanoclusters embedded within a silicon nitride matrix. Catalytic chemical vapor deposition was used to fabricate the embedded a-Si nanoclusters, and the formation of a-Si nanoclusters was confirmed by photoluminescence spectroscopy. The femtosecond laser interference technique was employed to produce a seed pattern for the spatially-selected crystallization of a-Si nanoclusters. Micro-Raman spectroscopy and selected-area electron diffraction, together with high-resolution transmission-electron microscopy, show that nanocrystalline silicon gratings were formed through an amorphous-to-crystalline transformation with femtosecond laser pulses, and that the degree of crystallization was enhanced by applying post thermal annealing to the seed gratings.