The nanocomposites on the base of Si nanocrystals (Si-nc) embedded into Al2O3 matrix are very promising for applications due to the outlook for light-emitting devices in optoelectronics. However, the luminescence yield controversially depends on structure of Si nanoinclusions, lattice defects of matrix, chemistry and stresses accommodation at interfaces. The physical ground of this phenomenon is connected with competition between radiative- and non-radiative transitions. Normally the non-radiative transitions reduce device efficiency by suppressing luminescence.
Si-nc were formed in the R- and C-plane sapphire substrates, and deposited Al2O3 films on Si substrate by Si+ ions implantation with doses ranging from 5x1016 to 3x1017 cm-2 at an energy 100 keV and post-implantation annealing at 500-1100 oC. The depth profiling measurements by XPS, HREELS investigations of interband electronic transitions, and EELFS analysis of accommodation strains have provided information on depth distribution of Si, impurities, matrix defects, and electrons transitions associated with radiative and non-radiative transitions. These experimental data allowed to understand an influence of Si+ ion implantation dose and annealing temperature on the luminescent properties of the fabricated nanocomposites. It was shown that the presence of defects at the Si-nc/Al2O3 interfaces originated from the accommodation stresses leads to severe degradation of the Si-nc's luminescence in the sapphire. The possible ways to overcome this difficulty are discussed.
Acknowledgements: The work has been supported by the European Commission through the FP6 project SEMINANO NMP4-CT-2004-505285, and by RF State Contract 3662p/4844 provided by FASIE.
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