Electron spin resonance observation of the Si(111)-(7x7) surface and its oxidation process

Electron spin resonance (ESR) observation of dangling-bond states on the Si(111)-(7x7) surface is demonstrated for the first time. The ESR spectra clearly show that a reaction of molecular oxygen with the Si(111)-(7x7) surface is associated with the appearance of a new dangling-bond center at unreacted Si adatoms. Most of the oxidized surface sites do not show ESR signals, but in a minor part of the surface another new type of surface defect is detected. The well known P(b) center at the SiO2/Si interface is found to evolve at an oxide thickness as thin as 0.3 nm.