Giant ( 12 × 12 ) and ( 4 × 8 ) reconstructions of the 6 H -SiC(0001) surface obtained by progressive enrichment in Si atoms

International audienceSilicon carbide (SiC) is nowadays a major material for applications in high power electronics, quantum optics, or nitride semiconductors growth. Mastering the surface of SiC substrate is crucial to obtain reproducible results. Previous studies on the 6H-SiC(0001) surface have determined several reconstructions, including the (√ 3× √ 3)-R30 • and the (3×3). Here, we introduce a process of progressive Si enrichment that leads to the formation of two reconstructions, the giant (12×12) and the (4×8). From electron diffraction and tunneling microscopy completed by molecular dynamics simulations, we build models introducing a type of Si adatom bridging two Si surface atoms. Using these Si bridges, we also propose a structure for two other reconstructions, the (2 √ 3×2 √ 3)-R30 • and the (2 √ 3×2 √ 13). We show that five reconstructions follow each other with Si coverage ranging from 1 and 1.444 monolayer. This result opens the way to greatly improve the control of 6H-SiC(0001) at the atomic scale