Abstract
We performed in situ scanning tunneling microscopy observation of oxygen reaction on the Si(111)7×7 surface at high temperatures. In spite of passive oxidation regime, we found that voids having the depth just one bilayer were formed at the initial stage of reaction. We found that the number density of the void was well represented by power laws. We applied the two-dimensional nucleation theory to this void formation and found that the critical nuclei were i = 1.46(647 K) and i = 14.7(751 K). We found the transition from active to passive oxidation with constant substrate temperature and oxygen exposure rate. The transition was quantitatively reproduced by the numerical simulations.
