Electron Energy Loss Spectroscopy in Analysis of Surfaces

Abstract

AbstractElectron energy loss spectroscopy (EELS) is a versatile and sensitive probe of electronic and vibrational excitations at surfaces. The technique is extensively used as a research and analytical tool in a broad range of surface science applications including research on intrinsic physical and chemical properties of surfaces, chemisorption phenomena, and chemical processes at surfaces. The spectroscopy is based on measuring the energy loss and momentum transfer of electrons in a highly collimated, monochromatic (narrow energy spread) beam after the electrons scatter from a surface. Vibrational excitations of atoms and molecules adsorbed on surfaces, collective excitations of ordered chemisorbed structures, the intrinsic collective excitations of surface atoms (surface phonons), and collective electronic excitations (surface plasmons) can be studied using the technique. Under favorable conditions, vibrational losses from surface adsorbate concentrations below 10−3monolayer (1012atoms cm−2) can be detected. EELS is a surface science probe, typically requiring an ultrahigh vacuum (UHV) environment, and is generally employed in conjunction with complementary surface analytical probes such as Auger electron spectroscopy (AES), low‐energy electron diffraction (LEED) and thermal desorption mass spectroscopy (TDS). EELS is an ideal tool for determining surface chemical composition, and provides vibrational loss spectra similar to infrared reflection absorption spectroscopy (IRAS), Raman spectroscopy, and helium atom scattering spectroscopy (HAS).