Fabrication, characterization, and application in nanoenergetic materials of uncracked nano porous silicon thick films

The porous silicon (PS) film has gained increasing attention in recent years as advanced nanoenergetic materials (nEMs). A simple fabrication method to prepare uncracked PS thick films was successfully realized with precisely controlled electrochemical etching, and the relationship between the current density and the concentration of electrolytes was found in its fabrication. Additionally, the capillary stresses resulted from the liquids in nanopores of PS films was another factor resulted in its crack. The nanopores composed of uncracked PS thick films distributed regularly and their diameters ranged from 2 nm to 6 nm. Its Sa (average roughness) of PS film surface was 6.53 nm, and its thickness ranged from 102.41 μm to 205.75 μm. The specific surface area was 587 m2/g and the average diameter of nanopores was 4.3 nm. The PS film was found to be monocrystal and it was same as the substrate. The crack mechanism of PS films was discussed: the porous structure reduced the strength of PS films comparing the silicon bulk and the capillary effect hastened the crack of PS films. PS films filling with sodium percholorate in nanopores were ignited by laser and the stable combustion showed that they were advantageous to be applied as micro-electromechanical systems (MEMS) compatible devices, such as silicon-based chips of mircothruster and microigniter.