Regensburg 2002 – scientific programme

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DS: Dünne Schichten

DS 21: Multilayer I

DS 21.2: Talk

Thursday, March 14, 2002, 14:15–14:30, HS 31

Synthesis and size-control of Si nanocrystals by SiO/SiO₂ superlattices — •Johannes Heitmann¹, Roland Scholz¹, Michael Schmidt², and Margit Zacharias¹ — ¹MPI für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany — ²Otto-von-Guericke Universität Magdeburg, Inst. für Experimentelle Physik, PF 4120, D-39016 Magdeburg, Germany

Todays Silicon nanocrystal research is focused on preparation of nanocrystals embedded in oxide host. Different processes for the synthesis of nanocrystalline Si like Si ion implantation into high-quality oxides, sputtering of Si-rich oxides or reactive evaporation of Si-rich oxides are known. Within these methods the Si crystal size is controlled by the Si content in the SiO₂ matrix. Therefore, crystal size and density cannot be controlled independently. We present a new approach of reactive evaporation of SiO/SiO₂ superlattices for nc-Si synthesis which allows independent control of these properties by adjusting the crystal size by the SiO layer thickness. TEM investigations confirm the thermal induced phase separation of the SiO layers in SiO₂ and Si nanocrystals and the correlation between SiO layer thickness and crystal size. A size-dependent blue shift of the luminescence from 900 to 750 nm and a luminescence intensity comparable to porous Si are observed. Temperature and power dependence of the luminescence intensity are reported. The nearly size-independent PL intensity observed in our SiO/SiO₂ superlattices indicates the accomplishment of an independent control of crystal size and density.