Preparation and characterization of mesoporous silicon spheres directly from MCM-48 and their response to ammonia

The synthesis process of mesoporous silicon spheres directly from MCM-48 through a metal thermal reduction reaction is presented. The MCM-48 spheres were reduced in vacuum at 620 A degrees C, with the spherical shape retained. The synthesized porous silicon spheres were confirmed as crystalline silicon by X-ray diffraction and transmission electron microscope. The silicon spheres have a microstructure different to those of etched silicon films by traditional method. The sample exhibited a slight red shift in PL spectrum after exposure to ammonia. This shift from 2.00 to 1.98 eV is ascribed to the Si-N adduct which disorder the space charge region in the semiconductor to weaken the quantum confinement effect. This design enables the syntheses of mesoporous nanocrystalline silicon spheres with multifarious three-dimensional shapes inherited from MCM-48 for sensor or optical applications.