7. SURFACE ANALYSIS BY MEANS OF IS

Surface analysis by means of IS consists of determining the elemental and chemical composition of near surface layers. The elemental composition is determined by:

• 7.1. Qualitative composition analysis technique
• 7.2. Standard samples technique
• 7.3. Elemental sensitivity coefficients technique
• 7.4. Analysis depth
• 7.5. Investigation of chemical bonding between the atoms

7.5. Investigation of chemical bonding between the atoms

Formation of chemical compounds causes redistribution of electric charges between the atoms. This changes binding energies Ec of the electrons on the core levels and also the empty states spectrum of the solid body, and therefore, the value of the ionization loss . The values of Ec and are changing simultaneously during the chemical reactions. The difference of values in simple and composite substance is called the chemical shift of IL, (), where and – are the losses during IL excitation of element A in the simple substance and in the chemical compound AB.

Experiments have proved the binding energy Ec and the chemical shift depend on the effective atomic charge . The dependency is the basis of structural formula identification by means of XPS technique in chemical copmounds, since it offers predictive capability [Ref 8].

The chemical shifts in IS are investigated in less detail than in XPS. The IS technique can be used for chemical compound identification only when the simple dependencies are empirically established, similarly to . As an example such dependencies were obtained for oxides and nitrides of silicon [Ref 2, Ref 3].

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