Shevchenko V. Porous silicon surface modification and its influence on the optical properties.

The dissertation is devoted to the elucidation of the processes occurring at the surface of nanoporous silicon exposed in the atmospheric and humid air as well as in water solution with different pH and solutions of polynucleic acids. It is shown that the conditions of porous silicon oxidation, such as the air humidity and the UV irradiation of the sample, affect the rate of oxide layer growth and the structure of the material. Existence of water with different energies of the hydrogen bond at the porous silicon surface is revealed by IR spectroscopy. The water state in porous silicon is determined by the conditions of growth and further treatment of the samples and influences on the process of the porous layer oxidation. It is shown that the photoluminescence is a sensitive tool for evaluation of the transformations in porous silicon. It is also shown that porous silicon luminescence intensity depends on the pH of a water solution. It is established that the porous silicon photoluminescence intensityrises when porous silicon contacts with solutions of polynucleic acids and that the intensity is sensitive to the different types of polynucleotide helical structures. A mechanism of the influence of polynucleotides on the porous silicon luminescence is considered.