Using scanning tunneling microscopy (STM) the atomic H adsorption on a Ag covered 6H-SiC(0001) surface was investigated. Ag deposition onto the 6H-SiC(0001)√3×√3 surface held at 500oC resulted in the formation of 3×3-Ag and 2D-island regions. STM images of the 3×3-Ag surface revealed one round protrusion per 3×3 unit cell at the empty state, while the protrusion showed a trimer like appearance at the filled state. As a result of atomic H adsorption at 300oC 2D layer of Ag was changed to 3D Ag clusters. Annealing of this surface at 500oC produced again 3×3-Ag and 2D-islands. However, the structures disappeared and the original √3×√3 surface was recovered by further annealing at 600oC. Thus, the reversible transformation from metal 2D layer to 3D clusters induced by atomic H adsorption was directly observed and evidenced in the case of SiC.
