Scattering Spectroscopy ISS

FIGURE 22. AES spectra of CRS both before (a) and after (b) sputtering 7 min. AES spectra of DQSK both before (c) and after (d) sputtering 7 min (sputter rate 1-2 A/min). Reprinted with permission from Reference 31. Copyright 1986 Gordon and Breach Science Publishers. 

FIGURE 23. Auger peak-to-peak height (APPH) vs. sputter time for oxygen (510 eV) and chromium (529 eV). (a) Sample had been decreased only, (b) treatment dichro-mate/sulfuric acid. Reprinted with permission from Reference 13. Copyright 19 83 But-terworth Scientific Ltd. 

FIGURE 24. Wedge test results vs. APPH ratio of chromium to iron. Reprinted with permission from Reference 13. Copyright 1983 Butterworth Scientific Ltd. 

ISS is most useful in the analysis of metal adherend surfaces as a characterization technique prior to bonding, or for analysis of failure surfaces. 

FIGURE 26. ISS spectra (a) from the original surface and (b) from the surface after stripping the gold. Reprinted with permission from Reference 33. Copyright 1981 Gordon and Breach Science Publishers. 

LEIS is attractive as a surface-specific technique. Spectra are usually obtained using noble gas ion beams from 0.5 to 3 keV. Due to strong electron affinity of inert-gas ions, the probability of electron transfer is very high, even in the initial collision with a surface atom. After two or more collisions, most ions are neutralized so that a detector set to analyze only ions of the same type as those in the incident beam detects ions that have almost entirely had only one collision with a target atom. Projectiles entering the solid are discarded because they require several scattering events to return to the surface and exit. 

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Ion Scattering Spectroscopy (ISS) is one of the most powerful and practical methods of surface analysis available. However, it is undemtilized due to a lack of understanding about its application and capabilities. This stems from its history, the limited number of high-performance instmments manufactured, and the small number of experienced surface scientists who have actually used ISS in extensive applications. Ironically, it is one of the easiest and most convenient sur ce analytical instruments to use and it provides usehil information for almost any type of solid material. 

In low energy ion scattering (LEIS, also called ion scattering spectroscopy, ISS) a beam of noble gas ions with energy of a few keV scatters elastically from a solid sur-... 

Secondary ion mass spectrometry (SIMS) Secondary neutral mass spectrometry (SNMS) Ion-scattering spectroscopy (ISS)... 

The tools available for surface composition characterization are electron spectroscopy for chemical analysis (ESCA), Auger spectroscopy (AES), ion scattering spectroscopy (ISS), and secondary ion mass spectroscopy (SIMS). ESCA spectroscopy is used more widely than the others for studying the surface composition and oxidation states of industrial catalysts, and thus its application will be discussed in limited detail. 

In situ methods permit the examination of the surface in its electrolytic environment with application of the electrode potential of choice. Usually they are favored for the study of surface layers. Spectroscopic methods working in the ultra high vacuum (UHV) are a valuable alternative. Their detailed information about the chemical composition of surface films makes them an almost inevitable tool for electrochemical research and corrosion studies. Methods like X-ray Photoelectron Spectroscopy (XPS), UV Photoelectron Spectroscopy (UPS), Auger Electron Spectroscopy (AES) and the Ion Spectroscopies as Ion Scattering Spectroscopy (ISS) and Rutherford Backscattering (RBS) have been applied to metal surfaces to study corrosion and passivity. 

Ion Scattering Spectroscopy (ISS) fig. 4 (12) shows the spectra of fresh and used a- b2C>4-Ma03 (50 50) catalysts two sets of measurements are made (two... 

Fig, 4. Ion Scattering Spectroscopy (ISS) measurements on a-Sb204-Mo03 50 50 mixtures fresh and after use, Ne+ tons of 2KeV were used. The fluence is the integrated ion dose. The surface concentrations (ordinates) are obtained thanks to calibration. It should be reminded that in ISS measurements, the first atomic layer is progressively removed by the ion bombardment, so that successive layers may be analysed. In the present case, a fluence of about 2.1015 ions/cm 2 is necessary to remove one monolayer of metal ions (12). 

The most popular of these are secondary ion mass spectroscopy (SIMS), ion scattering spectroscopy (ISS), and Auger electron spectroscopy (AES) which have been developed by investigators such as Baun, McDevitt, and Solomon.16-20 These tools have proved practical even when the surface films are only on the order of atomic dimensions or when the failure occurred near the original interface and included parts of both the adhesive and the adherend. 

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