Secondary mass analyzers

The instrumentation for SSIMS can be divided into two parts (a) the primary ion source in which the primary ions are generated, transported, and focused towards the sample and (b) the mass analyzer in which sputtered secondary ions are extracted, mass separated, and detected. 

The direct imaging magnetic sector mass analyzer (Fig. 3.19) has the unique property that all parts (lenses, electrostatic analyzer and magnetic sector field) of the secondary ion optics are stigmatic (comparable with light microscopes). This means that all points of the surface are simultaneously projected into the analyzer. 

There are now several different types of machines that are all capable of microanalysis. All have advantages and disadvantages, but the choice of which to use is often governed by expense and availability to a particular institution. Electron probe microanalysis is by far the most popular, but here particle-induced X-ray emission (PIXE), the laser microprobe mass analyzer (LAMMA), electron energy loss spectroscopy (EELS), and secondary ion mass spectrometry (SIMS) are also considered. 

Optical examination of etched polished surfaces or small particles can often identify compounds or different minerals hy shape, color, optical properties, and the response to various etching attempts. A semi-quantitative elemental analysis can he used for elements with atomic number greater than four by SEM equipped with X-ray fluorescence and various electron detectors. The electron probe microanalyzer and Auer microprobe also provide elemental analysis of small areas. The secondary ion mass spectroscope, laser microprobe mass analyzer, and Raman microprobe analyzer can identify elements, compounds, and molecules. Electron diffraction patterns can be obtained with the TEM to determine which crystalline compounds are present. Ferrography is used for the identification of wear particles in lubricating oils. 

The time-of-flight secondary ion mass spectroscopy (ToF-SIMS) analysis was performed on a CAMECA ION-TOF Model IV spectrometer. This instrument was equipped with a reflection-type ToF mass analyzer and a pulsed 25 kV primary... 

Improvements in solid mass spectrometry after the Second World War focused on the development of several types of ion source and mass analyzers. For example, the fundamentals of secondary ion mass spectrometry had already been described by the observation of secondary ions by Thomson in 1910 5 T had the occasion.. . to investigate the secondary Canalstrahlen produced when primary Canalstrahlen strike against a metal plate. Significantly later in 1949, the first instrumental arrangement for secondary ion mass spectrometric measurements was reported by Herzog and Viehbock.43 The idea of applying secondary ions for surface analysis was developed in 1950 at the RCA Laboratories, Princeton, where Honig44 presented results of early SIMS studies. 

ISOLDE at CERN (SC), make it feasible to consider using such secondary ions as projectiles for nuclear reactions. A pressing need for reaction rate data involving radioactive species exists in nuclear astrophysics. This requires having available projectiles (A < 60) in the energy range from about 200 keV/amu to 1.5 MeV/amu. It has been proposed to install an ISOL device at the TRIUMF facility to utilize the available intermediate energy (200-500 MeV), intense (<100 yA) proton beam as the primary production source. The mass analyzed, radioactive beam (RB),... 

The analytically important features of Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometry (1) have recently been reviewed (2-9) ultrahigh mass resolution (>1,000,000 at m/z. < 200) with accurate mass measurement even 1n gas chromatography/mass spectrometry experiments sensitive detection of low-volatility samples due to 1,000-fold lower source pressure than in other mass spectrometers versatile Ion sources (electron impact (El), self-chemical ionization (self-Cl), laser desorption (LD), secondary ionization (e.g., Cs+-bombardment), fast atom bombardment (FAB), and plasma desorption (e.g., 252cf fission) trapped-ion capability for study of ion-molecule reaction connectivities, kinetics, equilibria, and energetics and mass spectrometry/mass spectrometry (MS/MS) with a single mass analyzer and dual collision chamber. 

Ions Ion Scattering Mass Spectroscopy, Laser Microprobe Mass Analyzer, Rutherford Backscattering Spectroscopy, Secondary Ion Mass Spectroscopy. 

In 1967 Liebl reported the development of the first imaging SIMS instrument based on the principle of focused ion beam scanning [24]. This instrument, the ion microprobe mass analyzer, was produced by Applied Research Laboratories (Fig. 4.5). It used an improved hollow cathode duoplasmatron [25] ion source that eliminated filaments used in earlier sources and allowed stable operation with reactive gases. The primary ion beam was mass analyzed for beam purity and focused in a two-lens column to a spot as small as 2 pm. The secondary ions were accelerated from the sample surface into a double focusing mass spectrometer of Mattauch-Herzog geometry. Both positive and negative secondary ions were de-... 

Figure 5 Ion microprobe mass analyzer, first scanning-probe imaging secondary ion mass spectrometer (SIMS). (From Ref. 24.)...

At its simplest the secondary ion mass spectrometer needs only five elements. These are an ion source to create the bombarding primary ions, a target or sample holder, a mass analyzer for analysis of the secondary ions, a detector to transform the ions to recordable form, and a recording device. Usually, the practical SIMS... 

Fig. 1. Schematic diagram of a simplified FAB source (1) probe, (2) fast-atom beam, (3) atom gun, (4) sputtered secondary ion beam, (5) source ion optics, (6) to mass analyzer.

In SIMS a primary ion beam (1-20 keV) causes ejection (sputtering) of neutrals and ions from a solid specimen the secondary ions are mass-analyzed. In static mode, sampling is restricted to the first 1-3 atom layers at the surface by keeping the sputtering rate low (0.1 nm/hour). The ejected ions and ion clusters give information on the nature and may give clues to the chemical state of species present. 

Some spectra were recorded on a non-commercial SIMS instrument designed and built at EG G in Idaho Falls, ID. It has been described (13.141. Essentially, it is equipped with a primary source of SF6 neutrals and anions and a 0-2000 amu quadrupole mass analyzer. Qualitatively, the spectra obtained were identical to those of the commercial instrument, but the secondary ion yield was higher and charge neutralization was not required. 

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