Interactions of water vapor and oxygen with Si(111) surfaces studied by low-energy electron-loss spectroscopy

Low-energy electron-loss spectroscopy (ELS) has been applied for the studies of interactions of water vapor and oxygen with Si(111) 7×7 surfaces. It has been shown that ELS, due to its high surface sensitivity, is capable of observing the microscopic changes of the surfaces after adsorption, decomposition, desorption, and oxidation. The primary electron energy dependence of the loss spectra has shown a qualitative difference between oxygen-covered Si(111) and SiO2 surfaces. For SiO2 surfaces, the breakdown of the opticlike selection rule has been observed in the one-electron transitions at the low primary electron energies.