Chemical characterization of the uppermost layers.
Many important properties, such as adhesion, friction, oxidation, and optical behavior, are determined by a material’s chemical composition. Furthermore, these properties are determined by compositional differences that originate from different depths. For example, wettability, which influences adhesion and bonding, is determined almost exclusively by the composition of the outermost atomic layers. By contrast, oxidation processes are governed by compositional differences within the top 2 to 20 nm. The surface of a material is typically thought of as the top 10 – 100 nm. Surface analysis is primarily concerned with identifying the composition and/or morphology of the surface. In order to examine the properties of the surface in more detail, you both formulate the right analytical question for surface analysis and select the appropriate analytical method. For example, what is the objective of the analysis? What surface properties are of interest? What information depth is required? What lateral resolution is required?
Often customers will associate surface analysis with methods that have high lateral resolution for microanalysis such as Scanning Electron Microscopy (SEM) or Atomic Force Microscopy (AFM). These techniques can produce atomically sharp images and are useful for identifying the structure of materials; however, these techniques do not provide chemical information. In contrast, X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry provide chemical information on the top 10 – 100 nm. In addition, XPS and ToF-SIMS depth profiling can be used to characterize multilayer structures.