Morphology and Optical Characteristics of TiO2 Nanofilms Grown by Atomic-Layer Deposition on a Macroporous Silicon Substrate

A process for creating a macroporous silicon substrate on which a layer of titanium dioxide was deposited using the atomic-layer deposition method is described. Electrochemical etching was used to form the macroporous structure of the substrate. TiO₂ was deposited using an SI PEALD setup. The morphology, structure, and optical properties of the deposited TiO₂ film were assessed using scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy, spectral ellipsometry in the range 240–1000 nm, and Raman spectroscopy. Raman spectra revealed peaks at 144, 194, 397, and 639 cm^–1 that were characteristic of the TiO₂ anatase modification. The absorption coefficient and optical band gap width of the deposited film were determined based on the calculated ellipsometric parameters.