Ion beam synthesis of cubic-SiC layer on Si(111) substrate

We have investigated SiC layers produced by ion beam synthesis on Si(111) substrates using different procedures. Bare Si(111) and SiO₂/Si(111) structures were implanted with carbon at 40 keV up to a fluence of 4 × 10¹⁷ cm^-2 at a temperature of 600°C. Postimplantation annealing was carried out at 1250°C for 2 h in pure O₂ or Ar (with 1% of O₂). A SiC layer was synthesized for all the procedures involving annealing under Ar. However, for the samples annealed under pure O₂ flux, only that employing implantation into the bare Si(111) resulted in SiC synthesis. Rutherford backscattering spectrometry shows that, after annealing, the stoichiometric composition is obtained. Transmission electron microscopy measurements demonstrate the synthesis of cubic-SiC layers that are completely epitaxial to the Si(111) substrate. However, there is a high density of nanometric twins, stacking faults, and also narrow amorphous inclusions of laminar shape between the crystalline regions. The procedure based on high temperature implantation through a SiO₂ cap, etching the cap off, 1250°C postimplantation annealing under Ar ambient (with 1% of O ₂), and final etching has shown advantages from the point of view of surface flatness and increased layer thickness, keeping the same layer epitaxy and accurate composition.