Structural and electronic investigation of Si(0 0 1) surface after acetylene interaction

In this work we investigated the structural properties and photoluminescence (PL) of silicon carbide films grown in an ultra-high-vacuum (UHV) set-up by acetylene C2H2 carbonization of Si(0 0 1) surfaces. We used several UHV electron techniques to probe the local structural properties of the film and scanning tunneling microscopy (STM) to study its morphology. We followed two different growth procedures to obtain cubic 3C–SiC films: in the first case the substrate temperature is maintained at 650 °C during acetylene exposure while in the latter case room temperature exposure is followed by annealing performed at 1000 °C. Such a high temperature heating has been necessary to avoid the formation of both carbidic and graphitic environments that an annealing at lower temperatures (e.g. at 650 °C) has been evidenced. STM images showed the formation of cubic, ordered rather flat at atomic scale, nanostructures (of about 20 nm) arranged around deep, volcanoes rectangular-shaped holes. The PL spectra, recorded at 10 K, showed the presence of features typical of a Si1−xCx alloy containing around 1% or less of diluted carbon. This observation indicates that also in the case of a complete formation of cubic crystalline SiC it is impossible to avoid the coexistence with a substoichiometric alloy with carbon content of a few percent.