The influence of annealing on structural and photoluminescence properties of silicon-rich Al₂O₃ films prepared by co-sputtering

Si-rich Al₂O₃ films were produced by RF magnetron co-sputtering of pure silicon and alumina targets onto a long silicon oxide substrate. The effect of an annealing treatment on structure and light emission property of the films with different Si content was investigated by means of X-ray diffraction, Raman scattering and photoluminescence (PL) methods. The formation of amorphous Si clusters upon deposition process was observed for the films with Si volume content exceeded 70%. The annealing treatment of the films with Si content exceeded 80% results in the formation of Si crystallites with the mean size of about ∼14 nm. Three overlapped PL bands were detected in the 500-950 nm spectral range. The analysis of PL spectrum shape revealed that the near-infrared PL component, peaked at 850 nm, is caused by the exciton recombination inside Si crystallites. Another, the most intense PL band with maximum at 560-580 nm can be ascribed to defects in matrix located near nanocrystal/matrix interface, while the origin of the third PL band with the peak position at 700-750 nm is supposed to be also due to host defects whose nature requires more investigation.