Negative SIMS

Fig. 43. (A) Po.sitive and (B) negative SIMS. spectra of a plasma-polymerized acetylene film on a polished steel substrate. Reproduced by permission of Gordon and Breach Science Publishers from Ref. [56].

Negative SIMS spectra obtained from plasma polymerized acetylene films on polished steel substrates as a function of reaction time with the model rubber compound are shown in Fig. 45. The most important changes observed in the... 

SIMS Cluster Ion Characterization During Oxygen Adsorption and Oxidation. For heavy oxidation, that is essentially bulk oxide films, the oxidation state of the metal can be determined from the positive and negative SIMS intensity distributions (1 ). Though similar attempts have been made to characterize the nature of the surface during the early stages of oxygen interactions (14,15), we now know from the extensive information available from other techniques that such interpretations are incorrect. We use the by now well-characterized W(100)/O and Ni(100)/0 systems as examples. 

SSIMS has been applied to study of the chemical poisoning and thermal deactiviation of the catalyst that takes place with increasing distance travelled by the car. Figure 4.10 shows the positive and negative SIMS spectra obtained from a fresh fully formulated auto-exhaust system. 

Figure 9.4 Negative SIMS spectra in the mass ranges of 15-65 and 100-150 amu of a Rh/Al2(tyAl model catalyst prepared from RhCl3 x H20, after reduction at different temperatures. Note the disappearance of the RhCP signal after reduction at 200 °C, whereas significant signals from Cf and CKT are still observed (from Borg et at. (4 ).

Figure 9.26 Cr 2p spectra and negative SIMS spectra of two model catalysts and a blank reference. The blank (bottom) shows only Si,0, fragments on a chromium-loaded catalyst CriCf fragments appear after thermal activation (Ar/02). If desorption of chromium is made impossible (in oxygen-free argon), Cr2Or clusters can also be detected. In combination, this is strong evidence that chromate anchors to the silica surface as a monomer (courtesy of P.C. Thiine and R. Linke, Eindhoven).

SIMS is a technique of direct mass analysis where the ion sputter is removed from the surface and, as a result of the ion bombardment, it is analyzed. By measuring both positive and negative ions, two different types of mass spectra are obtained. Positive SIMS is especially sensitive to low Z elements, which have low electronegative and ionization potential, while the negative SIMS is most sensitive to low Z elements with high electronegativity. The SIMS spectrum shown in Fig. 2.14 (Denison et al., 1988a, b) as a function of mass number is typical of that obtained from a carbon fiber surface. 

Figure 6. Negative SIMS Spectra of Contaminated Quartz...

In order to characterize the extent of ion induced damage and the effect of attenuation of molecular emission by overlayer coverage a series of mixed multilayer systems were fabricated. The overall sample thickness was 5 LB layers (approx. 140 A), consisting of 4 layers of arachidic acid and 1 layer of behenic acid. Five permutations are then possible by altering the position of the behenic acid layer with respect to the substrate. The positive and negative SIMS results are summarized in Table 4. These results suggest that the molecular ions from different mechanisms result from different depths. 

Figure 3. Negative SIMS of formic acid frozen at 77 K...

Figure 5. Negative SIMS spectra of benzyne and cyclohexane frozen at 77 K (A) before and (B) after bombardment with a dose of 2 X 10 ions/cm of 100 eV Ng ...

Try to determine the ions in the negative SIMS spectrum of polystyrene in Figure 8.15. 

Double-chain surfactants with two sulfonate groups were proposed for micellar elec-trokinetic chromatography (MEC) analysis of phenolic pollutants in water °. CE with ESI-MS detection was applied to the analysis of phenolic compounds in olive mill wastewaters. Quantitative analysis was performed in the negative SIM mode, using p-chlorophenol as internal standard. LOD ranged from 1 pg for 4-hydroxybenzaldehyde and protocatechuic acid (27) to 386 pg for vanillic acid (38) °". A modified montmorillonite served for SPE preconcentration of phenols, followed by EtOH desorption and CE end analysis . 

Figure 14. Positive and negative SIMS of pyrimidine bases [103].

Table VI. Negative SIMS Peak minus Background Intensities...

Figure 3. Negative SIMS spectra from surface of alloy A which was exposed to the supernatant of human saliva for several hours.

Negative SIMS spectrum showing both elements and polyatomic fragments of molecules. [Courtesy of Physical Electronics USA, Inc. Eden Prairie, MN (www.phi.com).]... 

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