Atomic-scale self-propagation of a molecular reaction on a semiconductor surface:: O2/β-SiC(100)-3x2

The atomic-scale propagation of the reaction between molecules (O-2) and a semiconductor surface (silicon carbide) has been investigated by scanning tunneling microscopy. The results reveal a self-propagation reaction mechanism that gradually turns the initially inactive sites (>96% on the clean surface) into sites active to oxygen. This produces a patchwork of oxidized islands spreading over the surface. Numerical simulation of their growth (shape and dimension) as a function of further oxygen deposition supports such a self-propagation mechanism versus conventional nucleation-growth schemes.