Structural and optical properties of Si/β-FeSi 2 /Si heterostructures fabricated by Fe ion implantation and Si MBE

Abstract

The morphology and optical properties of Si samples implanted by low-energy Fe⁺ ions with different fluencies (1×10¹⁵ - 1.8×10¹⁷ cm^-2) and further subjected to pulsed ion-beam treatment (PIBT) have been studied by atomic force microscopy and optical reflectance spectroscopy. It was proved that the iron disilicide ( β-FeSi₂) crystallites have been formed on the surface of Si substrate as a result of ion implantation and PIBT. The method of ultrahigh vacuum and low-temperature (Τ = 850°C) cleaning of Fe⁺-implanted Si samples has been used for the first time. It was found that it is possible to form smooth epitaxial Si films with reconstructed surface and thickness up to 1.7 μm by molecular beam epitaxy (MBE) on the surface of Si samples implanted at a fluence of up to 1×10¹⁶ CM^-2. Further increasing implantation fluence results into disruption of epitaxial Si growth and strong increase of surface relief roughness due to 3D silicon growth mechanism. Preservation of β-FeSi₂ precipitates inside Si matrix after the formation of a cap epitaxial Si layer has been confirmed by optical spectroscopy data. Low temperature photoluminescence measurements in the range of 1400-1700 nm showed that light emission of the Si/ β-FeSi₂/Si heterostructures formed is due to contributions from β- FeSi₂ precipitates and dislocations.