Analysis Methods for Depth Profiling

The sensitivity to heavy elements means that RBS is an excellent method for depth profiling of heavy elements in polymers that are usually made up of H, C, O and N. In typical polymers, the depth resolution of RBS is about 30 nm. Park et al. [241] have described the use of RBS and XPS for the analysis... 

Some solid materials are very intractable to analysis by standard methods and cannot be easily vaporized or dissolved in common solvents. Glass, bone, dried paint, and archaeological samples are common examples. These materials would now be examined by laser ablation, a technique that produces an aerosol of particulate matter. The laser can be used in its defocused mode for surface profiling or in its focused mode for depth profiling. Interestingly, lasers can be used to vaporize even thermally labile materials through use of the matrix-assisted laser desorption ionization (MALDI) method variant. 

Initial results prove the high potential of LA-based hyphenated techniques for depth profiling of coatings and multilayer samples. These techniques can be used as complementary methods to other surface-analysis techniques. Probably the most reasonable application of laser ablation for depth profiling would be the range from a few tens of nanometers to a few tens of microns, a range which is difficult to analyze by other techniques, e. g. SIMS, SNMS,TXRE, GD-OES-MS, etc. The lateral and depth resolution of LA can both be improved by use of femtosecond lasers. 

There are two varieties of SIMS - static and dynamic. Static SIMS (often referred to as time-of-flight SIMS, TOF-SIMS) is often the method-of-choice, used for elemental analysis and imaging of the top two to three monolayers of a sample in comparison, dynamic SIMS is used to determine elemental concentrations of the sample, as a function of depth. As such, dynamic SIMS is a destructive technique primarily used for depth profiling, whereas TOF-SIMS does not appreciably deteriorate the surface being analyzed. For instance, due to a slow, controllable sputtering rate, the entire analysis may be performed without removing less than one-tenths of an atomic monolayer. 

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