Sputtering atomic spectroscopy

Bernhard A. E. (1987) Atomic absorption spectrometry using sputtering atomization of solid samples, Spectroscopy 2 118. 

The development by Muller (393) of the field ion microscope gave a considerable thrust to studying surface structures. In a recent modification of this technique, Panitz (394) designed a field desorption spectrometer that promises determination of the crystallographic distribution of species on metal surfaces. Secondary ion mass spectroscopy can also provide some quantitative information of surface species by sputtering atoms with an inert gas ion beam and detecting them by mass spectrometry. Submonolayers of adsorbed gases can be studied by this method (395). 

SNMS Spullered Neutral Mass Spectroscopy Surface, bulk Plasma discharge noble gases 0.5-20 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 > 3 depth prolile deleclion limit ppm 4,6... 

GDMS Glow Discharge Mass Spectroscopy Sample forms the cathode for a D.C. glow discharge Sputtered atoms ionized in plasma Ions - analyzed in mass spectrometer 0.1-100 pm 3-4 mm (Bulk) trace element analysis deleclion limit sub-ppb 9,10... 

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. 

Higashi, Y. (1999) Quantitative depth profiling by laser-ionization sputtered neutral mass spectrometry. Spectrochimica Acta Part B Atomic Spectroscopy, 54, 109-122. 

P. Hannaford Spectroscopy with sputtered atoms. Contemp. Phys. 24, 251... 

Evidence for the presence of core holes in sputtered atoms/ions can be identified in the spectra from several techniques, with the most direct being that of Ion-induced Auger Electron Spectroscopy (lAES). This is understood as lAES spectra arises from the de-excitation of core holes formed as a result of atomic collisions induced through energetic ion impact on the solid s surface of interest. De-excitation in the sputtered population is, however, only noted in spectra collected at close to glancing angles (reasons are outlined in Section 3.2.1.2). This is noted as ... 

During sputtering, the atoms can then be collisionally excited. These collisions may be with ions, electrons, or other atoms that have been previously excited by collisions with ions, electrons, or atoms. Once excited, atoms lose their energy very quickly. In optical atomic spectroscopy, the wavelength of this photon can be used to determine the identity of the atom, and the number of photons is directly proportional to the concentration of that element in the sample. Some collisions, which are of high energy, result in ionization. By atomic mass spectrometry, these ions are detected. Their mass identifies the type of atoms, and their quantity reveals the amount of that element in the sample. 

Use of glow-discharge and the related, but geometrically distinct, hoUow-cathode sources involves plasma-induced sputtering and excitation (93). Such sources are commonly employed as sources of resonance-line emission in atomic absorption spectroscopy. The analyte is vaporized in a flame at 2000—3400 K. Absorption of the plasma source light in the flame indicates the presence and amount of specific elements (86). 

Auger electron spectroscopy (AES) is a technique used to identify the elemental composition, and in many cases, the chemical bonding of the atoms in the surface region of solid samples. It can be combined with ion-beam sputtering to remove material from the surface and to continue to monitor the composition and chemistry of the remaining surface as this surface moves into the sample. It uses an electron beam as a probe of the sample surface and its output is the energy distribution of the secondary electrons released by the probe beam from the sample, although only the Ai er electron component of the secondaries is used in the analysis. 

Since ion beams (like electron beams) can be readily focussed and deflected on a sample so that chemical composition imaging is possible. The sputtered particles largely originate from the top one or two atom layers of a surface, so that SIMS is a surface specific technique and it provides information on a depth scale comparable with other surface spectroscopies. 

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