Secondary Ion Mass Spectrometry for Surface Analysis

Secondary ion mass spectrometry (SIMS) is a relatively new technique for surface chemical analysis compared with Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). SIMS examines the mass of ions, instead of energy of electrons, escaped from a solid surface to obtain information on surface chemistry. The term secondary ion is used to distinguish primary ion that is the energy source for knocking out ions from a solid surface. The advantages of SIMS over electron spectroscopy are  

Such features make SIMS a powerful technique for surface analysis. However, SIMS as a surface analysis technique has not yet reached a mature stage because it is still under development in both theoretical and experimental aspects. This lack of maturity is attributed to the complicated nature of secondary ion yield from a solid surface. Complexity of ion yield means that SIMS is less likely to be used for quantitative analysis because the intensity of secondary ions is not a simple function of chemical concentrations at the solid surface. SIMS can be either destructive or non-destructive to the surface being analyzed. The destructive type is called dynamic SIMS it is particularly useful for depth profiling of chemistry. The nondestructive type is called static SIMS. Both types of SIMS instruments are widely used for surface chemical examination. 

Materials Characterization Yang Leng 2008 John Wiley Sons (Asia) Re Ltd 

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The emission of positive ions, which are for example used in the SIMS method (secondary ion mass spectrometry) for surface analysis, is unimportant in the sputtering process. Owing to the high negative potential, positive ions do not come away from the target surface. 

The surface of the particles can be studied directly by the use of electron microprobe X-ray emission spectrometry (EMP), electron spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy (AES), and secondary ion-mass spectrometry. Depth-profile analysis determines the variation of chemical composition below the original surface. 

Environment. Detection of environmental degradation products of nerve agents directly from the surface of plant leaves using static secondary ion mass spectrometry (sims) has been demonstrated (97). Pinacolylmethylphosphonic acid (PMPA), isopropylmethylphosphonic acid (IMPA), and ethylmethylphosphonic acid (EMPA) were spiked from aqueous samples onto philodendron leaves prior to analysis by static sims. The minimum detection limits on philodendron leaves were estimated to be between 40 and 0.4 ng/mm for PMPA and IMPA and between 40 and 4 ng/mm for EMPA. Sims analyses of IMPA adsorbed on 10 different crop leaves were also performed in order to investigate general apphcabiflty of static sims for... 

This assumes that the gas-solid exchange kinetics at the interface is rapid. When this process affects the exchange kinetics significantly dieii analysis of concentrations layer by layer in die diffused sample is necessaty. This can be done by the use of SIMS (secondary ion mass spectrometry) and the equation used by Kihier, Steele and co-workers for this diffusion study employs a surface exchange component. 

Sputtered Neutral Mass Spectrometry (SNMS) is the mass spectrometric analysis of sputtered atoms ejected from a solid surface by energetic ion bombardment. The sputtered atoms are ionized for mass spectrometric analysis by a mechanism separate from the sputtering atomization. As such, SNMS is complementary to Secondary Ion Mass Spectrometry (SIMS), which is the mass spectrometric analysis of sputtered ions, as distinct from sputtered atoms. The forte of SNMS analysis, compared to SIMS, is the accurate measurement of concentration depth profiles through chemically complex thin-film structures, including interfaces, with excellent depth resolution and to trace concentration levels. Genetically both SALI and GDMS are specific examples of SNMS. In this article we concentrate on post ionization only by electron impact. 

In other articles in this section, a method of analysis is described called Secondary Ion Mass Spectrometry (SIMS), in which material is sputtered from a surface using an ion beam and the minor components that are ejected as positive or negative ions are analyzed by a mass spectrometer. Over the past few years, methods that post-ion-ize the major neutral components ejected from surfaces under ion-beam or laser bombardment have been introduced because of the improved quantitative aspects obtainable by analyzing the major ejected channel. These techniques include SALI, Sputter-Initiated Resonance Ionization Spectroscopy (SIRIS), and Sputtered Neutral Mass Spectrometry (SNMS) or electron-gas post-ionization. Post-ionization techniques for surface analysis have received widespread interest because of their increased sensitivity, compared to more traditional surface analysis techniques, such as X-Ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES), and their more reliable quantitation, compared to SIMS. 

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

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