Fabrication and Characterization of Monolithic 3D Amorphous Silicon Inverse-opal Photonic Materials with Magnesiothermic Reduction at a Lower Temperature

Background: Silicon photonic structures (PSs) with inverse opal structures are favored due to their high refractive index at optical frequencies. However, the fabrication of monoliths of 3D amorphous silicon (a-Si) inverse opals with large band-gaps and photoluminescence at optical frequencies especially in the visible range is rarely reported in literatures. Methods: The monoliths of the ordered 3D polystyrene colloidal crystals are immersed into tetraethyl-orthosilicate solution for several hours and then dried. The resulting monolith of latex/silica is calcinated under an oxygen flow. Using the porous silica as templates and reactants, a-Si photonic structures with a face centered cubic crystal lattice are obtained through a magnesiothermic reduction procedure. Results: Large-scale monoliths of a-Si photonic materials with inverse opal macro-porous hierarchical nanostructures have been fabricated. This successful fabrication is mainly attributed to the lower-temperature (605 ºC) and the disordered amorphous morphology for Si. The obtained 3D a-Si inverse opals are with a full band-gap at optical frequencies. Conclusion: This facile fabrication of large-scale amorphous Si photonic materials with well-tailored optical properties would greatly extend the applications of a-Si in optoelectronics and other fields.