Analytical techniques surface analysis methods

This Chapter mainly deals with the big four surface analysis techniques (XPS, AES, SIMS, ISS). For spatially resolved surface analytical methodologies, cfr. Chps. 3 and 5. Various surface analysis methods provide images of elements and other information (cfr. Chp. 5.9). Eor surface studies by means of IR spectroscopies, cfr. Chp. 1. 

Nowadays it is becoming common practice to bring multiple analytical techniques to bear on the characterization of catalysts. Very often bulk and surface analysis methods are combined to yield detailed complementary information. A typical scheme of catalyst parameters to be determined and of appropriate analytical methods has been presented by Delmon [ I). who reviewed the potential of surface analysis in the characterization of hydrodesulfurization (HDS) catalysts. This scheme, redrawn, is shown in Fig. 1. Unfortunately, due to certain inherent problems, the whole range of well-e.stablished surface spectro.scopic methods cannot be applied in every case. Another disadvantage is that the application of surface-specific spectroscopies requires the transfer of catalyst samples into vacuum, thus restricting the possibilities for genuine in situ surface analysis of working catalyst.s. 

The predorninant method for the analysis of alurninum-base alloys is spark source emission spectroscopy. SoHd metal samples are sparked direcdy, simultaneously eroding the metal surface, vaporizing the metal, and exciting the atomic vapor to emit light ia proportion to the amount of material present. Standard spark emission analytical techniques are described in ASTM ElOl, E607, E1251 and E716 (36). A wide variety of weU-characterized soHd reference materials are available from major aluminum producers for instmment caUbration. 

Laser desorption methods (such as LD-ITMS) are indicated as cost-saving real-time techniques for the near future. In a single laser shot, the LDI technique coupled with Fourier-transform mass spectrometry (FTMS) can provide detailed chemical information on the polymeric molecular structure, and is a tool for direct determination of additives and contaminants in polymers. This offers new analytical capabilities to solve problems in research, development, engineering, production, technical support, competitor product analysis, and defect analysis. Laser desorption techniques are limited to surface analysis and do not allow quantitation, but exhibit superior analyte selectivity. 

The reluctance of museum curators and collectors to allow permanent damage to antiquities was, until not long ago, the main reason for the small amount of analytical work done on ancient coins. This was understandable since performing chemical analysis required removing a sample from the coin or damaging its surface, which meant either the destruction or defacement of, at least, a portion of a coin. More recently, however, a number of nondestructive methods of analysis such as neutron activation, X-ray fluorescence, and some techniques of surface analysis have been successfully applied to obtain information about ancient coins and the people and societies involved in their production (Carter 1993 Barrandon et al. 1977). 

Brands proposed a calculation method in the case of segregation A special type of inhomogeneous, particulate objects is the surface analysis by microscopic techniques e.g. analytical electron sj troscopy, laser induced mass spectroscopy or proton-induced X-ray emission. Here the minimum sample size can be translated into the minimum number of specific sample points in the specimen under investigation. 

The most frequently applied analytical methods used for characterizing bulk and layered systems (wafers and layers for microelectronics see the example in the schematic on the right-hand side) are summarized in Figure 9.4. Besides mass spectrometric techniques there are a multitude of alternative powerful analytical techniques for characterizing such multi-layered systems. The analytical methods used for determining trace and ultratrace elements in, for example, high purity materials for microelectronic applications include AAS (atomic absorption spectrometry), XRF (X-ray fluorescence analysis), ICP-OES (optical emission spectroscopy with inductively coupled plasma), NAA (neutron activation analysis) and others. For the characterization of layered systems or for the determination of surface contamination, XPS (X-ray photon electron spectroscopy), SEM-EDX (secondary electron microscopy combined with energy disperse X-ray analysis) and... 

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