Fabrication and optical characterization of Nanopore Si

We have fabricated nanotextured Si substrates that exhibit controllable optical reflection intensities and colors. Si Nanopore, which has photon-trapping nanostructure but has abrupt changes in the index of refraction displaying a darkened specular reflection. Aluminum is evaporated on the surface of N-type Si by e-beam evaporation. Nanopore structure is formed by a two-step AAO formation in oxalyic acid. Diameter size from 30 to 80 nm is achieved, depending on the condition of anodization and etch. Deep reactive ionic etch (DRIE) is done, with AAO as the mask layer. The nanopore AAO template allows etching depth of up to 1600 nm. By tuning the nanoscale silicon structure, the optical reflection peak wavelength and intensity are changed, making the surface to have different reflectivity and apparent colors. Parameters that affect the fabrication are evaluated. Optical properties of various pore depths are discussed. The relation between the surface optical properties with the spatial features of the photon trapping nanostructures is examined. The tunable photon trapping silicon structures have potential applications in enhancing the performance of semiconductor photoelectric devices.