Transformation of porous structure under vacuum ultraviolet irradiation of the films based on silicon dioxide

Transformation of the films with the pores of different radii under the action of vacuum ultraviolet radiation was studied experimentally and theoretically. Simulation results showed that Si–O–Si angle depends on pore size. Fourier Transform infrared spectra provide indirect confirmation of this statement. The experimental data and calculation results suggest that methyl group decreases π bonding, which causes a decrease in Si–O–Si angle. The action of ultraviolet radiation is to be considered as a photochemical reaction; the fragments formed in this reaction (CH₃^⁎, CH₂^⁎) can participate in polymerization, which leads to pore sealing. - Highlights: • Irradiation with the energy of 10–20 eV causes pore sealing. • FTIR studies and simulation results show that Si–O–Si angle depends on pore size. • Fragments formed in photochemical reaction (CH₂^⁎) can participate in polymerization. • Polymerization probability is high because the process takes place in closed space.