Optical properties of a nanoporous array in silicon

Abstract

We demonstrate an approach for producing an array of nanopores on a silicon surface. The methods used combine nonlithographic pattern transfer and chlorine plasma etching to produce ∼60nm diam holes up to 1μm in depth. The near-normal specular optical reflectance of these systematically modified surfaces is found to decrease dramatically with pore depth across the entire 2.0–6.0eV photon energy range studied. We adapt an effective medium approximation to model specular reflectance taking into account diffuse scattering by the nanopatterned surface. Micro-Raman measurements show a systematic intensity increase with pore depth. The observed dependence suggests that both insertion and extraction are enhanced by the nanopatterning.