Si(111)2x2-Fe surface reacted with nitric oxide

We have studied a Si(111)2x2-Fe surface exposed to nitric oxide at room temperature with Auger electron spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy (STM). The surface local structure of Si(111)2x2-Fe has been modeled to be similar to that of Si(111)7x7; both structures have Si adatom and Si first-layer restatom, but the restatom in the former surface bonds to Fe atoms. It is known that NO molecules dissociatively adsorb on Si(111)7x7 surface, especially atop adatoms. Before the exposure to the Si(111)2x2-Fe surface, STM images showed 2x2 islands on the 2x2 terrace. After the exposure, the 2x2 islands were eroded at the island edge while the 2x2 terrace was stable against nitric oxide. We ascribed the inert property of the 2x2 terrace, and the reactive property of the 2x2 island edges and the 7x7 terrace, primarily to the Si restatom with different neighbor atoms