High Energy Secondary Ions

IV.Ic) High energy secondary ions Very often, the decrease in secondary ion intensities with increasing secondary ion energy is much greater for molecular ions than for atomic ions. Therefore, discrimination against molecular ions can be... 

Figure 19 Positive SIMS spectra from oxygen-bombarded steel (a) low and (b) high energy secondary ions monitored (from Ref. 2).

McKeegan, K.D., Coath, C.D., Jarzebinski, G., Kunihiro, T., Mao, P.H. (2005) MegaSIMS a high energy secondary ion mass spectrometer for the analysis of captured solar wind. Microscopy and Microanalysis, 11,1376-1377. 

Adsorbates on solid electrode surfaces can also be examined by MS if they are removed from the surface by bombardment with a high-energy primary ion beam. The species removed are secondary ions derived from the surface constituents and are detected by the mass analyser (Fig. 12.12). Thus the technique is referred to as secondary ion mass spectrometry (SIMS). It turns out that sensitivity is greater than with AES or XPS. The obvious disadvantage is the destruction of the top layers of the solid and implantation in the solid of ions used in the bombardment. 

MALDI-IMS is still limited to about 20 pm spatial resolution (with 10-50 pm the most commonly achievable spatial resolution at this time), typically obtained with commercial ion sources (80). Recently, Zavalin et al. demonstrated that 5 pm spatial resolution can be achieved for MALDI-IMS instruments by spatial filtration of the laser beam by using a 25 pm ceramic pinhole filter (81). Secondary ion mass spectrometry (SIMS), developed in the 1960s (82), offers a complementary or alternative method to MALDI-IMS and other matrix-free LDI-MS methods for the acquisition of higher spatial resolution images. In SIMS, a focused high-energy primary ion beam (such as Cs+, Au3+, Bi5+, or C60+) is used to directly bombard the sample... 

Also of interest to electrochemistry is SIMS, which is another ex situ UHV method for surface and thin-film characterization (93, 103, 128, 129). This approach involves the bombardment of a surface with a high-energy primary ion beam (e.g., 15 keV Cs" ), which etches the surface by sputtering and produces secondary ions derived from the sur-... 

Metson, J.B., Tui, D.L., Muir, I.J., Bancroft, G.M. (1988) High energy secondaries for the quantitative secondary ion mass spectrometric analysis of minerals. Scanning Microsc., 2, 663-670. 

Della Negra S and Le Beyec Y (1983) Secondary ion emission from surfaces of solids bombarded by high energy heavy ions. Applications in analytical mass spectrometry and studies with beams from accelerators. Nuclear Science Applications 1 569-590. 

Secondary ion mass spectroscopy (SIMS) utilizes a high-energy primary ion beam to sputter and eject secondary ions from solid surfaces. The ejected ions are analyzed with a mass spectrometer. Elemental and chemical information can be obtained. The SIMS also has excellent spatial resolution. 

Fig. 3.21. SIMS spectra obtained from a high-speed steei. (A) primary ions OJ no secondary ion energy iimitation eiec-tropositive eiements are sensitive many moiecuie ions are visibie. (B) same conditions but 300 Voffset was used the moiecuie ion intensities are reduced significantiy. (C) Primary ions Cs" 300 Voffset was used therefore eiectronegative eiements are detected more sen-sit iveiy.

Physically the generation of X-rays is often a secondary process preceded hy the ionization of an atom. There are, therefore, several possihilities of X-ray generation depending on the type of the exciting medium - neutrals or charged particles such as electrons and ions and high-energy photons, i. e. X-rays themselves. 

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