Fabrication and optical properties of 3D composite photonic crystals of core–shell structures

Three-dimensional (3D) composite colloidal photonic crystals with SiO2 core and ZnO shell were fabricated on borosilicate glass (BSG) substrate by a two-stage deposition method. Scanning electron microscopy (SEM) measurements show that both the pre-deposited SiO2 and SiO2/ ZnO core–shell structures are oriented with their (1 1 1) axes parallel to the substrates. Optical measurement reveals that the periodic arrays exhibit a photonic band gap in the (1 1 1) direction. The optical properties of SiO2/ZnO core–shell structures strongly depend on the size dispersions of colloidal spheres and the intrinsic defects in the sample