Glow discharge OES

Tab. 11. Detection limits ( tg/g) for steels in spark and glow discharge OES and glow discharge MS.

Figure 7.44 A GD sputter spot in a steel sample showing the uniform removal of the surface. It is this uniform sputtering process that permits accurate depth profiling of layered materials hy glow discharge OES. [Courtesy of LECO Corporation, St. Joseph, MI (www.leco.com).]...

Fig. 4.36. Diagram of a typical glow discharge device used for GD-OES depth profiling [4.189].

In conclusion, GD-OE S is a very versatile analytical technique which is still in a state of rapid technical development. In particular, the introduction of rf sources for non-conductive materials has opened up new areas of application. Further development of more advanced techniques, e. g. pulsed glow discharge operation combined with time-gated detection [4.217], is likely to improve the analytical capabilities of GD-OE S in the near future. 

Several recent reviews deal with GD-OES [157,162, 163] and pulsed glow discharge [164,165]. Several books on GDS have appeared [158,166,167]. 

FF-TLC Forced-flow TLC GD-OES Glow-discharge-optical emission... 

GD-OES (glow discharge optical emission spectrometry) are applied. AES (auger electron spectroscopy), AFM (atomic force microscopy) and TRXF (transmission reflection X-ray fluorescence analysis) have been successfully used, especially in the semiconductor industry and in materials research. 

Today, as a direct solid-state analytical technique, dc GDMS is more frequently applied for multi-element determination of trace contaminants, mostly of high purity metallic bulk samples (or of alloys) especially for process control in industrial laboratories. The capability of GDMS in comparison to GD-OES (glow discharge optical emission spectrometry) is demonstrated in a round robin test for trace and ultratrace analysis on pure copper materials.17 All mass spectrometric laboratories in this round robin test used the GDMS VG 9000 as the instrument, but for several... 

A depth profile analysis of trace and matrix elements (B, Na, Ni, Fe, Mg, V, A1 and C) in a 26p.m Si layer on a SiC substrate measured by GDMS, yielded impurity profiles, for example, with constant Ni contamination in the Si layer and enrichment at the interface layer.45 However, with respect to depth profiling of thin layers using dc GDMS with a depth resolution between 50 and 500 nm, this technique plays a subordinate role compared to the commercially available and cheaper GD-OES (glow discharge optical emission spectrometry). 

Three techniques with spatially resolved information capabilities have been selected here for some further explanation EPXMA, laser-induced breakdown spectroscopy (LIBS) and glow discharge optical emission spectrometry (GD-OES). Figure 1.15 summarises the lateral and depth resolution provided by the techniques described in this section. It is worth noting that the closer to the bottom left corner the technique is located, the higher (and so better) is the depth resolution. 

The microwave-induced plasma (MIP) is the most popular plasma used for conventional GC-OES. However, the DC glow discharge plasma has recently received more attention because it can be operated at a low temperature, albeit at a low pressure 1-30 Torr so as to avoid excessive gas heating and arcing. 

Figure 4.4 Optical emission spectra (OES) measured from (A) dissociation glow and (B) negative glow in DC glow discharge of trimethylsilane (TMS) flow system, 1 seem TMS, 50 mtorr, DC power 5 W.

Figure 4.5 The time dependence of emission intensity of various photo-emitting species detected by OES in TMS DC glow discharge in a closed reactor (a) polymerizable species in dissociation glow, (b) Hoc emission line at 656 nm 50 mtorr TMS, DC power 5 W.

Figure 4.6 Dissociation glow and ionization glow in DC glow discharge of TMS and respective OES species material forming species are mainly in the dissociation glow and the ionization glow consists of mainly hydrogen species.

Knowledge of the atomic spectra is also very important so as to be able to select interference-free analysis lines for a given element in a well-defined matrix at a certain concentration level. To do this, wavelength atlases or spectral cards for the different sources can be used, as they have been published for arcs and sparks, glow discharges and inductively coupled plasma atomic emission spectrometry (see earlier). In the case of ICP-OES, for example, an atlas with spectral scans around a large number of prominent analytical lines [329] is available, as well as tables with normalized intensities and critical concentrations for atomic emission spectrometers with different spectral bandwidths for a large number of these measured ICP line intensities, and also for intensities calculated from arc and spark tables [334]. The problem of the selection of interference-free lines in any case is much more complex than in AAS or AFS work. 

Fig. 107. Determination of Si in Al alloys with medium voltage spark OES (A) and OES using a Grimm-type glow discharge (B). [480],...

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