Solid-state decomposition of silicon carbide for growing ultra-thin heteroepitaxial graphite films
Résumé
Using grazing-incidence x-ray diffraction and scanning tunneling microscopy STM, we show that the thermal decomposition of an electronic-grade wafer of 6H-SiC after annealing at increasing temperatures T A between 1080 and 1320 °C leads to the layer-by-layer growth of unconstrained, heteroepitaxial single-crystalline graphite. The limited width of the in-plane diffraction rod profiles of graphite reveals large terraces, with an average size larger than 200 Å and a very small azimuthal disorientation. The overlayer is unstrained and adopts the crystalline parameter of bulk graphite even at the smallest coverage studied, which corresponds to a single graphene plane, as inferred from the flat out-of-plane diffraction profile. By increasing T A , additional graphene planes can be grown below this graphite layer from the solid-state decomposition of SiC, forming the AB stacking of Bernal graphite. A C-rich precursor is evidenced in STM by an intrinsic 66 reconstruction made of ordered ring or starlike structures. The resulting epitaxial film is indistinguishable from a bulk graphite single crystal.