Vibrational electron energy loss spectroscopy of the Si(111)(7×7)–H2O(D2O) system

Abstract

High-resolution electron energy loss spectroscopy (EELS) has been applied to the study of the Si(111)(7×7)–H2O(D2O) system. At 300 K, H2O(D2O) is partially dissociated on the Si(111) surface to form the SiOH(SiOD) and SiH(SiD) species. Angle and primary-electron-energy dependences of the vibrational loss intensities were measured. Relative contributions to the vibrational excitations of the dipole, impact, and resonance mechanisms were estimated. The O–H(O–D) stretching and Si–O–H (Si–O–D) bending vibrations are partly excited by the resonance mechanism in the primary energy region of Ep ≂2–7 eV. EELS spectra of the Si(111) surface exposed to H2O(D2O) at 300 K and of the same surface heated to ∼700–900 K are presented, and surface reaction mechanisms are discussed.