Multi-functionalization of silicon by nanoparticles through "plug and play" approach

In this paper, we demonstrate a "Plug and Play" approach, whereby externally synthesized nanoparticles of desired functions and size are incorporated into the semiconductor, followed by the manipulation of surface chemical bonds in order to achieve multiple functionality. Sonochemically synthesised Fe₂O₃ nanoparticles were introduced onto device quality Si wafers. On annealing the particle-treated Si wafer in ultra high vacuum, oxygen changes the bonding partner from Fe to Si and desorb as SiO at ∼ 760°C, leading to the formation of uniform sized Fe nanoparticles (size ∼6-8 nm) on the surface and the sample shows ferromagnetic behaviour. More importantly, the particle treated Si exhibits light emission at wavelengths 1.57, 1.67 and 1.65 microns (full width at half maximum ∼ 20 meV). Emission in this wavelength range is crucial for optical communications and is highly desired from a Si based material. Further, oxidation of this material leads to the formation of a selective capping layer of SiO₂. Thus, by manipulating the surface chemical bonds,we are able to introduce optical, magnetic, metallic and insulating functions to Si. Additionally, the particles exhibits self-assembly on a patterned Si surface. We believe that this approach is universal and the material developed here is compatible with the planar Si technology, bringing us closer or realization of Si based monolithic electronics.