Characterization of Organic Surfaces

Abstract

This paper reviews the surface science techniques that appear most suitable for characterizing organic surfaces. We discuss 13 techniques, many of them developed in recent years, that provide information about composition and structure on the molecular level: secondary ion mass spectroscopy (SIMS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), low-energy electron diffraction (LEED), high-resolution energy electron loss spectroscopy (HREELS), Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FT-IR), sum frequency generation (SFG), scanning tunneling microscopy (STM), atomic force microscopy (AFM), surface force measurements (SFM), contact angle measurements, and neutron reflectivity measurements. The first two techniques, SIMS and XPS, provide information about surface composition and the chemical environment and bonding of surface species. UPS probes the density of electronic states in the valence band of materials and can provide a spectroscopic fingerprint of many organic compounds. LEED and HREELS are electron-scattering techniques that are uniquely suited to yield the structure of the surface monolayer. RS, FT-IR, and SFG are optical techniques used to study solid-gas interfaces at high pressures along with solid-solid and solid-liquid [open quotes]buried[close quotes] interfaces. STM, AFM, and SFM provide atomic-scale resolution of surface structure, the forces between molecules at surfaces and, in some cases, measurements of hardnessmore » and friction properties of the surface region. 34 refs., 22 figs.« less