Surface Analysis - The Analytical Method

In order to examine the properties of the surface in more detail, you must identify the appropriate analytical method. No analysis technique can determine all properties of a surface. Before beginning the analysis, it is important to formulate the right analytical question. What is the objective of the analysis? Which surface properties should be determined? What depth information is required? What depth resolution is required? What lateral resolution is required?

What is surface analysis used for?

Since our laboratory is primarily concerned with surface chemistry and surface morphology, customers often have the following questions:

• What species are present on the surface?
• Where are the species located?
• How much is present?

In order to select the most suitable analytical technique, the analyst must consider both the sampling depth (information depth) and the lateral resolution. The lateral resolution is defined as the ability to distinguish two points as separate in space. It is comparable to the smallest pixel size of an image that can be detected by the sensor of a digital camera and therefore determines how crispness of the chemical maps of a surface.

No technique can analyze a surface at all depths; therefore, the technique must be able to reliably answer the analytical question(s) of interest.

How does surface analysis work?

Surface analysis works on the principle of probing or bombarding the sample surface with energized atoms, ions, electrons or photons. The surface itself will respond with the emission of atoms, ions, electrons or photons. Depending on the type of ion or ion energy, electron energy, wavelength of the photons, UV light or X-ray quanta used in the analysis, you get different information about the surface properties.

The individual techniques for surface analysis provide different information about the surface. For example, some techniques such as Optical Profilometry or Scanning Electron Microscopy (SEM) provide primarily physical information such as surface roughness and morphology. In contrast, other techniques such as X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), or Low-Energy Ion Scattering (LEIS) provide chemical information.

The depth of information of the respective analysis technique is also important when selecting the appropriate analysis technique. For example, Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (SEM/EDX) and X-ray Photoelectron Spectroscopy (XPS) can both provide information on the elemental composition of a sample. However, the sampling depth of SEM/EDX is about 1 µm, while the sampling depth of XPS is 10 nm.

Tascon – your partner for surface analysis

Many customers initially assocaite surface analysis with methods that have a high lateral resolution for microanalysis and nanoanalysis such as Scanning Electron Microscopy (SEM) or Atomic Force Microscopy (AFM). These techniques can produce atomically sharp images and are useful for elucidating the structure of materials. However, these methods generally do not provide chemical information. Laboratory methods that provide chemical information often have lower lateral resolution. Laboratories which specialize in surface characterization must weight these options when choosing the appropriate surface analysis technique. Contact Tascon where our experienced and competent staff can help you select the analytical technique best suited to answering your analytical question. In order to have a look at what is not currently visible in surface analysis, it is best to ask an accredited test laboratory for surface analysis. The tested and competent staff there can best estimate which aspects of the surface could also play a role, which areas of the surface you should look at with other methods of surface analysis. If you have any questions about surface analysis, simply contact Tascon.