HIGH TEMPERATURE ANNEALING INFLUENCE ON STRUCTURE AND COMPOSITION OF a-Si/ZrO2 AND a-SiOx/ZrO2 MULTILAYERED NANOPERIODICAL STRUCTURES BY SYNCHROTRON XANES INVESTIGATIONS

Abstract

With the use of high brilliance synchrotron radiation the composition and structure of a-Si/ZrO2 and a-SiOx/ZrO2 multilayered nanoperiodical structures subjected to high temperature annealing were investigated. Each ZrO2 layers thickness was 2 nm while for a-Si or a-SiOx layers thickness was 8 nm with total number of layers 34 (a-Si/ZrO2) and 43 (a-SiOx/ZrO2). Annealing was performed for 30 minutes at temperatures from 500 °С to 1100 °С. X-ray absorption near edge structure spectroscopy technique was applied for detecting information about local partial density of free electronic states in conduction band relative to K core level of silicon with probing depth of about 65 nm. This technique is very sensitive to the local surrounding of given atoms (silicon in our case). It was shown that initial (not annealed) structures of both types contained elementary silicon and different silicon suboxides with oxidation degree less than 2. Annealing in 500 °С - 900 °С temperature range resulted in elementary silicon appearance in multilayered nanoperiodical structures but without silicon nanocrystals formation. Annealing at 1100 °С led to increasing of ordering in silicon atoms relative positions. Synchrotron X-rays absorption near edge fi ne structures relative intensity distribution did not reveal spectral features that are specifi c for ZrSiO4 silicates formation. Moreover the indirect evidence of zirconium silicide ZrSi2 formation for a-Si/ZrO2 multilayered nanoperiodical structures was observed after their annealing at 1100 °С.

Keywords

• multilayer nano periodal structures
• nanocrystals
• silicon
• silicon oxides
• electronic structure
• phase composition
• synchrotron radiation
• XANES.