Properties of Al_2O_3 : ne-Si Nanostructures Formed by Implantation of Silicon Ions into Sapphire and Amorphous Films of Aluminum Oxide

摘要

Photoluminescence, infrared Fourier spectroscopy, Raman scattering, transmission electron microscopy, and electron diffraction were used to study the luminescent, optical, and structural properties of aluminum oxide layers (sapphire and films of Al_2O_3 deposited on silicon) implanted with Si~+ to produce silicon nanocrystals. It is established that, in both cases, a high-temperature annealing of heavily implanted samples brings about the formation of silicon nanocrystals. However, the luminescent properties of the nanocrystals are strongly dependent on the type of pristine matrix; namely, nanocrystals in Al_2O_3 films emit light in the spectral range typical of Si quantum dots (700-850 nm), whereas in sapphire this photoluminescence is not observed. This difference is interpreted as being due to the fact that local stresses arise in the nanocrystal/sapphire system and break chemical bonds at the interface between the phases, whereas in Al_2O_3 films stresses are relaxed.