Sputtered neutral mass spectroscopy SNMS

The superior corrosion performance and strong adhesion of the plasma coating system can be attributed to the coating properties and, more importantly, to the nature of interfacial chemistry. Two techniques were applied to study the surface and interfacial chemistry of the plasma coating system (1) in situ plasma deposition and XPS analysis and (2) in-depth profiling of sputtered neutral mass spectroscopy (SNMS). 

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. 

Another important characteristic is that ion beams can produce a variety of the secondary particles/photons such as secondary ions/atoms, electrons, positrons. X-rays, gamma rays, and so on, which enable us to use ion beams as analytical probes. Ion beam analyses are characterized by the respectively detected secondary species, such as secondary ion mass spectrometry (SIMS), sputtered neutral mass spectrometry (SNMS), electron spectroscopy, particle-induced X-ray emission (PIXE), nuclear reaction analyses (NRA), positron emission tomography (PET), and so on. 

Sputtered neutral mass spectrometry (SNMS) depth profiles document that carbon is present in the skin of all fibers to a depth of about 50 nm (Figure 15), whether a given fiber has a secondary carbon sheath overgrowth or not [11]. X-ray photoelectron spectroscopy (XPS)... 

SNMS Sputtered Neutral Mass Spectroscopy Surface, bulk Plasma discharge noble gases 0.6-20 keV Sputtered atoms ionized by atoms or electrons then mass analyzed 0.1-0.6 nm (or deeper ion milling) 1 cm Elemental analysis Z a 3 depth profile deleclion limit ppm 4.6... 

There are several methods available to probe the actual interphase to demonstrate the existence of interpenetrating networks directly. Among these techniques are depth profiling by SIMS (secondary ion mass spectrometry) or SNMS (sputtered neutral mass spectrometry), and the use of X-ray photoelectron spectroscopy (XPS) depth profiling or Auger electron spectroscopy (AES) depth profiling. 

FIGURE 40.18 Depth profiles by laser secondary neutral mass spectrometry (laser SNMS), secondary ion mass spectrometry (SIMS) with Ar and 02 primary ions, and Auger electron spectroscopy (AES) of implanted boron. Reprinted from Higashi, Y., Quantitative depth profiling by laser-ionization sputtered neutral mass spectrometry (1999) Spectrochimica Acta Part B Atomic Spectroscopy, 54(1), 109-122. Copyright (1999), with permission from Elsevier Science. 

There are several MS-based techniques that can provide chemical information for thin and thick layers [12]. For very thin layers (sub to 1-2 monolayers), nondestructive techniques such as static SIMS [13], ion scattering MS [14], or MS of recoiled ions [15] are suitable. These techniques are also the best adapted for examining surface contamination. They are all based on surface interactions of an ion beam with the solid surface. For depth profiling of thin and thick layers, MS is associated with a destructive source of neutrals or ions dynamic SIMS, secondary neutron mass spectroscopy (SNMS), glow discharge mass spectroscopy (GD-MS), matrix-enhanced SIMS, laser desorption/ionization MS, and desorption electrospray ionization (DESI) MS [16]. Ions are either desorbed from the solid surface or generated by postionization of neutrals sputtered off the surface. 

Resonant and non-resonant laser post-ionization of sputtered uranium atoms using SIRIS (sputtered initited resonance ionization spectroscopy) and SNMS (secondary neutral mass spectrometry) in one instrument for the characterization of sub-pm sized single microparticles was suggested by Erdmann et al.94 Resonant ionization mass spectrometry allows a selective and sensitive isotope analysis without isobaric interferences as demonstrated for the ultratrace analysis of plutonium from bulk samples.94 Unfortunately, no instrumental equipment combining both techniques is commercially available. 

SNMS Secondary (sputtered) neutral (ion) mass spectroscopy... 

A high percentage of the sputtered secondary particles are neutral and must be post-ionized for mass spectroscopy analysis (SNMS) (62). Post-ionization can be achieved by electron impact in a plasma or by an electron beam. Alternatively, resonant and nonresonant laser ionization can be applied. Applications of SNMS for catalyst characterization have still not been reported. 

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