Fig. 1
From: Room Temperature Crystallization of Hydroxyapatite in Porous Silicon Structures
a Schematic illustration for growth of HA nanoparticles on PS by co-precipitation method. b Mixing of reactant for nucleation of HA. c Meso- and macroporous silicon substrate used to crystallize HA nanoparticles. Substrate roughness dependent formation of different morphologies of the crystals grown from the pore corners is explained in terms of the minimization of the surface free energy of the Si/SiO2 porous fractal surface as a result of the pore formation