SIMS Secondary Ion Mass Spectroscopy

SIMS yields compositional information for both surface characterization prior to bonding and for failure surface analysis. 

FIGURE 29. SIMS spectra of titanium-6-4 etched in hydrofluoric acid/ammonium orthophosphate for 30 sec (b) and titanium-6-4 etched in the same acid mixture for 180 sec (a). Reprinted with permission from Reference 33. Copyright 1981 Gordon and Breach Science Publishers. 

Secondary ion mass spectroscopy (SIMS) is a valuable technique for identifying the structure and composition of polymer surfaces and complements ESCA. Similar spectra are difficult to resolve by ESCA, while SIMS can differentiate among different polymers. This is partly due to the smaller sampling depth required by SIMS. In atypical analysis, the surface of the polymer sample is bombarded by a primary ion at low current density, mainly intended to minimize alteration of the sample surface. A polymer surface generates positive and negative ions that are analyzed using a mass analyzer. The results of detailed analysis provide chemical structure and composition information about the surface. A traditional shortcoming of SIMS is its inability to perform quantitative analysis. 

A different type of analyzer called Time of Flight (TOF) SIMS can be utilized to determine the structure of the sample as a function of sampling depth. TOF SIMS can be useful in determining stratification of resins in coatings or diffusion of atoms into a part underneath a surface. 

In this technique the sample surface is bombarded by a primary ion beam (positive ions of argon, caesium, oxygen or gallium). These primary ions impart energy to the surface and, as a consequence of the collisions produced, ions, atoms and molecular fragments (called sputtered particles) are ejected. The primary ions may penetrate several atom layers into the surface, but the sputtered particles only come from the outer 2-3 atom layers. In common with the other two techniques, therefore, SIMS is very surface specific and it is possible to restrict it to a single monolayer. The analysis area is typically 150 pm, the detection limit is 1 ppm and all the elements are detectable. 

Two types of SIMS experiment can be carried out static SIMS and dynamic SIMS. In the former case, the surface is bombarded with low energy ions and molecular and atomic fragments are produced without the experiment changing the nature of the surface appreciably the surface chemistry can therefore be investigated. Dynamic SIMS uses high energy ions to obtain highly sensitive elemental data down to ppb levels, but the structural information is lost. 

In the case of static SIMS, dedicated libraries are required to enable the mass spectra of the fragments to be identified (a.22). 

Another application of SIMS is in the study of the migration of additives (e.g., slip additives and antistats) onto the surface of plastics. 

It is often the case that complementary surface analysis techniques such as SIMS and XPS can be used together in order to successfully solve a failure or characterisation problem. In such cases, XPS would be used to generate quantitative information, whilst SIMS would provide qualitative clues with respect to the chemistry. An example of this is where XPS has successfully detected and quantified silicon on a surface which is not responding well to bonding with an adhesive, but the chemical form that the silicon is in is not readily apparent, i.e., it could be silica, silicate or silicone. Analysis of the same surface by static SIMS enables the mass spectmm of the sputtered top layer fragments to be determined and ihe presence of m/e ions at 43,73 and 147 confirm that a polydimethyl siloxane is present. 

Quantitative analysis of organic materials by TOF-SIMS is intrinsically difficult because of flieir tendency to decompose under ion irradiation. Techniques have, however, been devised to circumvent radiation-induced degradation. In a study, principal component analysis (PCA) was applied as a means of compensation for the spectral degradation caused by this decomposition and this improved the accuracy of the quantitative analysis. 

Two organic additives were used that had quite different composition and vulnerability to decomposition under ion irradiation in polystyrene. This enabled the extraction of a principal component related to their content that is independent of the decomposition. It proved the effectiveness of the approach in quantitative analysis of organic additives content in polymers without loss in accuracy due to spectral degradation. 

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Secondary Ion Mass Spectroscopy (SIMS). When the p-n junction and the GaAs/GaAlAs heterojunction are not coincident, carrier recombination occurs, reducing the current and the performance of fabricated heterojunction bipolar transistors. 

The main experimental techniques used to study the failure processes at the scale of a chain have involved the use of deuterated polymers, particularly copolymers, at the interface and the measurement of the amounts of the deuterated copolymers at each of the fracture surfaces. The presence and quantity of the deuterated copolymer has typically been measured using forward recoil ion scattering (FRES) or secondary ion mass spectroscopy (SIMS). The technique was originally used in a study of the effects of placing polystyrene-polymethyl methacrylate (PS-PMMA) block copolymers of total molecular weight of 200,000 Da at an interface between polyphenylene ether (PPE or PPO) and PMMA copolymers [1]. The PS block is miscible in the PPE. The use of copolymers where just the PS block was deuterated and copolymers where just the PMMA block was deuterated showed that, when the interface was fractured, the copolymer molecules all broke close to their junction points The basic idea of this technique is shown in Fig, I. 

The interface properties can usually be independently measured by a number of spectroscopic and surface analysis techniques such as secondary ion mass spectroscopy (SIMS), X-ray photoelectron spectroscopy (XPS), specular neutron reflection (SNR), forward recoil spectroscopy (FRES), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), infrared (IR) and several other methods. Theoretical and computer simulation methods can also be used to evaluate H t). Thus, we assume for each interface that we have the ability to measure H t) at different times and that the function is well defined in terms of microscopic properties. 

The most widely used techniques for surface analysis are Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), Raman and infrared spectroscopy, and contact angle measurement. Some of these techniques have the ability to determine the composition of the outermost atomic layers, although each technique possesses its own special advantages and disadvantages. 

X-ray scattering studies at a renewed pc-Ag/electrolyte interface366,823 provide evidence for assuming that fast relaxation and diffu-sional processes are probable at a renewed Sn + Pb alloy surface. Investigations by secondary-ion mass spectroscopy (SIMS) of the Pb concentration profile in a thin Sn + Pb alloy surface layer show that the concentration penetration depth in the solid phase is on the order of 0.2 pm, which leads to an estimate of a surface diffusion coefficient for Pb atoms in the Sn + Pb alloy surface layer on the order of 10"13 to lCT12 cm2 s i 820 ( p,emicai analysis by electron spectroscopy for chemical analysis (ESCA) and Auger ofjust-renewed Sn + Pb alloy surfaces in a vacuum confirms that enrichment with Pb of the surface layer is probable.810... 

Benninghoven, A., Surface Investigation of Solids by the Static Mmethod of Secondary Ion Mass Spectroscopy (SIMS), Surf Set., Vol. 35,1973, pp. 427-457. 

We will first consider, however, Secondary Ion Mass Spectroscopy (SIMS) in which both neutral and charged species are sputtered from the surface, and detected by means of a mass spectrometer. This involves ion beams of lower energy than in the techniques described previously. 

Ion beam probes are used in a wide range of techniques, including Secondary Ion Mass Spectroscopy (SIMS), Rutherford backscattering spectroscopy (RBS) and proton-induced X-ray emission (PIXE). The applications of these and number of other uses of ion beam probes are discussed. 

William Schopf studied supercrustal rock samples from Akilia Raman and ion microscopic photographs showed the presence of carbon-containing inclusions in grains of apatite. The carbon isotope ratio was determined by secondary ion mass spectroscopy (SIMS) the 813C value was -29% 4%, in agreement with earlier analyses. This in turn confirmed the values obtained by Mojzsis (1996), which had been questioned by Lepland et al. three years later. The final verdict on the oldest fossils in western Greenland may not be reached for several years yet (McKeegan et al., 2007 Eiler, 2007). 

Martin RR, Zanin JP, Bensette M J, Lee M, Furimsky E. Metals in the annual rings of eastern white pine (Pinus strobus) in southwestern Ontario by secondary ion mass spectroscopy (SIMS). Can J For Res 1997 27 16-19. 

Secondary intrinsic magnetic properties, of M-type ferrites, 11 67, 68 Secondary ion mass spectroscopy (SIMS), 24 74. See also SIMS entries archaeological materials, 5 744 Secondary ions, measurement of, 24 107 Secondary lead, 14 756-760 developments related to, 14 760 Secondary mercury production, end-uses and sources for, 16 39-42 Secondary metabolites... 

SIMS instrumentation, 24 108-109. See also Secondary ion mass spectroscopy (SIMS)... 

The way in which fluoride is taken up by glass-ionomers has been studied using surface analysis techniques. Dynamic secondary ion mass spectroscopy (SIMS) shows that most of the fluoride becomes concentrated in the surface [248]. Its concentration with depth varies as an error function relationship [248]. X-ray photoelectron spectroscopy (XPS) has suggested that fluoride taken up becomes associated with calcium [249]. However, the form of this association is unclear, because calcium fluoride as such is very insoluble, and when added to a fluoride-free glass-ionomer cement, caused no fluoride to be released [234]. It therefore seems unlikely that the calcium-fluoride association results in formation of Cap2, and further research is necessary to determine the precise nature of the calcium-fluoride association, and thus to resolve this paradox. 

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