Surface analysis methods spectroscopy

Analysis of Surface Elemental Composition. A very important class of surface analysis methods derives from the desire to understand what elements reside at the surface or in the near-surface region of a material. The most common techniques used for deterrnination of elemental composition are the electron spectroscopies in which electrons or x-rays are used to stimulate either electron or x-ray emission from the atoms in the surface (or near-surface region) of the sample. These electrons or x-rays are emitted with energies characteristic of the energy levels of the atoms from which they came, and therefore, contain elemental information about the surface. Only the most important electron spectroscopies will be discussed here, although an array of techniques based on either the excitation of surfaces with or the collection of electrons from the surface have been developed for the elucidation of specific information about surfaces and interfaces. 

Table 8 shows results obtained from the application of various bulk and surface analysis methods to lithium metal at rest or after cyclization experiments, as well as at inert and carbon electrodes after cathodic polarization. The analytical methods include elemental analysis, X-ray photoelectron spectroscopy (XPS or ESCA), energy-dispersive analysis of X-rays (X-ray mi-... 

GDS instruments are viable alternatives to the traditional arc and spark-source spectroscopies for bulk metals analysis. Advantages of GDS over surface analysis methods such as AES, XPS and SIMS are that an ultrahigh vacuum is not needed and the sputtering rate is relatively high. In surface analysis, GD-OES, AES, XPS and SIMS will remain complementary techniques. GD-OES analysis is faster than AES (typically 10 s vs. 15 min). GD-OES is also 100 times more sensitive than... 

Studies of molecular adsorption from solution at well-defined solid surfaces is yielding important results. Well-defined surfaces have a simplifying effect on such studies by eliminating many of the structural imperfections which would otherwise complicate the results with a mixutre of adsorption states. Surface analysis methods such as LEED, Auger spectroscopy, EELS, XPS and voltammetry are very well suited to the characterization of surface molecular structure, composition, and bonding. As a result, clear correlations between adsorbed state and surface chemical or electrochemical reactivity are beginning to emerge. 

It is evident from the above discussion that catalyst characterization is an activity important for scientific understanding, design, and troubleshooting of catalyzed processes. There is no universal recipe as to which characterization methods are more expedient than others. In the opinion of the writer, we will see continued good use of diffraction methods and electron microscopy, surface analysis, IR spectroscopy, and chemisorption methods, increased use of combined EM and ESCA analyses for determining the dopant dispersion, increased use of MAS-NMR and Raman spectroscopies for understanding of solid state chemistry of catalysts, and perhaps an increased use of methods that probe into the electronic structure of catalysts, including theory. 

Ellipsometry is probably the only easy-to-use surface analysis method which can be operated in situ and in real time. On the contrary, multiple internal reflection Fourier transform infrared spectroscopy is a very powerful technique [38] but it is rather tricky to implement. Ellipsometry allows real time studies of the surface modification during exposure to the plasma, and after the treatment. Figure 10 shows for example the variation of and A ellipsometry angles upon fluorination of Si in fluorine-based plasmas as a function of pressure and gas mixture [39], thus demonstrating the sensitivity of the technique. Infrared ellipsometry has also been used with success to investigate reaction layer composition and formation on Si in CF4-based plasmas [40,41], or to monitor patterning [42]. 

To combine optical SFG spectroscopy with the more traditional surface analysis methods (e.g., LEED, AES, TPD, XPS), the basic requirement is to simply add IR-transparent windows (e.g., CaF2 or BaF2) to a UHV chamber. However, if SFG spectroscopy is to be carried out at high pressure or during catalytic reactions, instruments combining a EIHV surface analysis system with an SFG-compatible... 

Ion Spectroscopies for Surface Analysis (Methods of Surface Characterization), Czanderna, A. W Hercules, D. M. eds., Springer New York, 1991. 

A. Joshi, L.E. Davis, and P.W. Palmberg. Auger Electron Spectroscopy. In A.W. Czandema, editor. Methods of Surface Analysis. Methods and Phenomena Their Applications in Science and Technology, Volume 1. Elsevier, New York, 1975. 

N.K. Roberts. Fourier Transform Infrared Spectroscopy of Surfaces. In D.J. O Conner, B.A. Sexton, and R. St. C. Smart, editors. Surface Analysis Methods in Materials Science. Springer Series in Surface Sciences, Volume 23. Springer-Verlag, Berlin, 1992. 

C.J. Powell, D.M. Hercules, and A.W. Czandema. Comparison of SIMS. SNMS, ISS, RBS, AES, and XPS Methods for Surface Compositional Analysis. In A.W. Czandema and D.M. Hercules, editors. Ion Spectroscopies for Surface Analysis. Methods of Surface Characterization, Volume 2. Plenum Press, New York, 1991. 

In this section we will outline the basic methodology of the plasma treatment process. First, the theory behind plasma treatment will be presented. Following this, experimental protocol outlining the treatment process, pertinent parameters, and their relevance will be discussed. Finally, surface analysis methods for plasma-treated surfaces will be described, such as X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measuring tools. 

Czanderna, A. W., Ion Spectroscopies for Surface Analysis, The Application of Surface Analysis Methods to Environmental/ Material Interactions, The Electrochemical Society, Pennington, NJ, 1991. 

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. 

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