Optical properties of thick ordered mesoporous silica membranes

Mesoporous silicon membranes with very uniform and vertical pores are fabricated by electrochemical anodization resulting in pore diameters between 15‐30 nm and pore depths of 550 μm. The influence of applied current density on the pore morphology is characterized for the formation of mesoporous silicon membranes. These porous silicon membranes are thermally oxidized to form transparent silica membranes. The current study involved ellipsometric measurements of the optical properties of porous silica material spectroscopically from 300 nm to 1000 nm. Normal transmittance through the membrane was measured and found to be attenuated significantly at short wavelengths but approached the transmittance of bulk silicon for the near infrared. Angularly resolved transmission and reflection study is performed extending into the infrared regime. Refractive index and extinction coefficients are modeled based on the optical measurements. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)