Neutron activation analysis electronics materials

The most frequently applied analytical methods used for characterizing bulk and layered systems (wafers and layers for microelectronics see the example in the schematic on the right-hand side) are summarized in Figure 9.4. Besides mass spectrometric techniques there are a multitude of alternative powerful analytical techniques for characterizing such multi-layered systems. The analytical methods used for determining trace and ultratrace elements in, for example, high purity materials for microelectronic applications include AAS (atomic absorption spectrometry), XRF (X-ray fluorescence analysis), ICP-OES (optical emission spectroscopy with inductively coupled plasma), NAA (neutron activation analysis) and others. For the characterization of layered systems or for the determination of surface contamination, XPS (X-ray photon electron spectroscopy), SEM-EDX (secondary electron microscopy combined with energy disperse X-ray analysis) and... 

Moreover the energies of these ( -partides (electrons) are known to be 1.39 MeV and that of the gamma-rays 1.38 MeV so that the measnned values of these magnitudes are characteristic of substances containing sodium. (Measurement of the y-radiadon is the usual procedure.) At least 70 of the elements can be activated in this way, by the capture of thermal neutrons, i.e.. by neutron activation analysis. An activation analysis follows a procedure similar to that shown ill Fig. 2. In almost all analyses, the sample materials are not treated before the bombardment, but are placed directly into the bombardment capsule or container. The length of the bombardment interval is usually determined by the half-life of the radionuclide used for the element of interest and the flux of nuclear particles. 

A multifaceted characterization effort to stndy these materials as a function of thermal treatment has been undertaken. The techniques include BET surface area measurements. X-ray diffraction, chemisorption, scanning and high-resolution transmission electron microscopy, analytical electron microscopy, neutron activation analysis, atomic absorption spectroscopy, FTIR and isotopic tracer studies. The details of catalyst preparation have been previously... 

A variety of analytic techniques currently are used to provide chemical characterizations of archaeological materials. These techniques which include instrumental neutron activation analysis (INAA), X-ray fluorescence (XRF), proton induced X-ray emission (PIXE), X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma-atomic emission )ectroscopy (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-... 

Cadmium concentrations in biological materials can also be measured with neutron activation analysis (NAA) and X-ray fluorescence spectroscopy (XRF). Both techniques depend on the detection of photons generated in cadmium by an externally incident beam of radiation. In NAA, the cadmium concentration in the sample is determined by studying the emission of y-rays after the irradiation of the sample with neutrons [33,34]. In contrast, photon emission in XRF is produced by an incident beam of X-rays or y-rays interacting with the atomic electrons of cadmium, resulting in the emission of characteristic X-rays [34]. 

Techniques for analysis of different mercury species in biological samples and abiotic materials include atomic absorption, cold vapor atomic fluorescence spectrometry, gas-liquid chromatography with electron capture detection, neutron activation, and inductively coupled plasma mass spectrometry. Methylmercury concentrations in marine biological tissues are detected at concentrations as low as 10.0 p,g Hg/kg tissue using graphite furnace sample preparation techniques and atomic absorption spectrometry. 

Introduction Unlike isotope measurement methods, there are several competing approaches available for the compositional elemental analysis of archaeological materials, including X-ray fluorescence, electron (or ion) naicroprobe analysis, or neutron activation. Each approach has its relative merits in terms of performance, spatial resolution, time and cost, and degree of destructiveness of the sample. 

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