Study of the Vibrational Modes of Subsurface Oxygen on Al (111) Using Diode Laser Infrared Reflection-Absorption Spectroscopy

摘要

Infrared reflection absorption spectroscopy (IRRAS), using polarization modulation and tunable diode laser excitation, has been applied to the study of the vibrational modes of subsurface oxygen on A1 (111). The dependence of the spectra on O2 exposure and on annealing has been investigated at a resolution of about 10-20/cm (1.2-2.5 meV) and correlated with Auger data. The absorption band (780-920/cm) consists of overlapping bands at about 835 and 862/cm associated, respectively, with isolated sites and with clusters of such sites resembling A1203. The apparent shift of this band to higher energy with increasing coverage, observed at lower resolution (but higher sensitivity) in electron energy loss spectroscopy, is found to result from the change in relative intensity of the two modes.