Oxidation of H-terminated Si(100) surfaces studied by high-resolution electron energy loss spectroscopy

Abstract

The adsorption of oxygen on H-terminated Si(100) surfaces has been investigated by high-resolution electron energy loss spectroscopy (HREELS). Adsorptions of atomic oxygen occur even at room temperature. Si-OH stretching and Si-O-Si (B1) vibrational modes are observed in HREELS spectra, which indicates that atomic oxygen is adsorbed on sites of Si—H bonds and Si—Si back bonds. On the other hand, H-terminated surfaces are very stable for molecular oxygen, which cannot adsorb until 380 °C on the surface. A dissociative adsorption of molecular oxygen is observed above 380 °C and the activation energy of the adsorption is 2.0 eV at 380–450 °C. This value coincides with the desorption energy of hydrogen atoms from a Si(100) surface with the monohydride phase. These results indicate that the dangling bonds are essential to the adsorption of molecular oxygen on Si(100) surfaces.