Surface Chemistry - Analysis Techniques

Analysis Techniques

The study and analysis of surfaces involves both physical and chemical analysis techniques.

Several modern methods probe the topmost 1–10 nm of surfaces exposed to vacuum. These include X-ray photoelectron spectroscopy, Auger electron spectroscopy, low-energy electron diffraction, electron energy loss spectroscopy, thermal desorption spectroscopy, ion scattering spectroscopy, secondary ion mass spectrometry, Dual polarization interferometry, and other surface analysis methods included in the list of materials analysis methods. Many of these techniques require vacuum as they rely on the detection of electrons or ions emitted from the surface under study. Moreover, in general ultra high vacuum, in the range of 10−7 pascal pressure or better, is necessary to reduce surface contamination by residual gas, by reducing the number of molecules reaching the sample over a given time period. At 0.1 mPa (10−6 Torr), it only takes 1 second to cover a surface with a contaminant, so much lower pressures are needed for measurements.

Purely optical techniques can be used to study interfaces under a wide variety of conditions. Reflection-absorption infrared, dual polarisation interferometry, surface enhanced Raman, and sum frequency generation spectroscopies can be used to probe solid–vacuum as well as solid–gas, solid–liquid, and liquid–gas surfaces. Dual Polarization Interferometry is used to quantify the order and disruption in birefringent thin films. This has been used, for example, to study the formation of lipid bilayers and their interaction with membrane proteins.

Modern physical analysis methods include scanning-tunneling microscopy (STM) and a family of methods descended from it. These microscopies have considerably increased the ability and desire of surface scientists to measure the physical structure of many surfaces. This increase is related to a more general interest in nanotechnology.