Nuclear Reaction Analysis depth profiling

Fig. 5. Hydrogen depth profile of a deuterated polystyrene PS(D) film deposited on a protonated polystyrene PS(H) film on top of a silicon wafer as obtained by l5N-nuclear reaction analysis ( 5N-NRA). The small hydrogen peak at the surface is due to contamination (probably water) of the surface. The sharp interface between PS(D) and PS(H) is smeared by the experimental resolution (approx. 10 nm at a depth of 80 nm) [57], The solid line is a guide for the eye...

Nuclear reaction analysis (NRA). Based on the detection of charged particles emitted during nuclear reaction, NRA can be considered as an inelastic counterpart of RBS. NRA is useful in the reverse case as for RBS, namely the depth profiling light elements in a sample composed of heavy elements, (e.g. corroded layers on metallic samples containing O, C, and N). Incident ions are protons ( H) or deuterons (2H). 

PIGE is very sensitive (the limit of detection can be as low as 1 ppm) and non-destructive. It allows analysis of bulk F, F-distribution within one sample on cross-sections or depth profiles using resonant nuclear reaction analysis (RNRA) [35]. The spatial resolution, even using a beam of some micrometres size or RNRA, is however insufficient to detect F on individual bone crystals. The RNRA method is reviewed in detail in the chapter of Dobeli et al. [6] in this volume. 

For all these specialty polymers, deuterium can be used as a label on one or the other monomer. Deuterium labeling allows the use of techniques based on ion detection such as forward recoil spectrometry (FRES), nuclear reaction analysis (NRA) or secondary ion mass spectrometry (SIMS). If a high-resolution depth profile of the interfacial region is needed, neutron reflectivity can also be used. The main drawback of that approach is the cost of the deuterated polymers while deuterated styrene and methyl methacrylate are expensive but commercially available, other monomers need to be synthesized and the cost can be quite prohibitive. 

Spatial features of the brush profile are observed with the precision determined by the resolution p of depth profiling techniques used. The resolution p, described as a half width at half maximum (HWHM) of a Gaussian function, should be at least comparable with the unperturbed dimension of the brush, characterized by its radius of gyration Rg(N). Therefore nuclear reaction analysis [19] (NRA, p=8 nm), secondary ion mass spectroscopy [26, 27] (SIMS, p=... 

Nuclear reaction analysis (NRA) and elastic recoil detection (ERD) are part of the suit of ion beam analysis (IBA) techniques. They are commonly used for the elemental depth profiling of materials in a wide range of fields, e.g., from biological and medical to the semiconductor industry. 

The most commonly used accelerator-based techniques for depth profiling are Rutherford Backscattering (RBS) which will be discussed in Chap. 2, Elastic Recoil Detection (ERD) which will be discussed in Chap. 3, and Nuclear Reaction Analysis (NRA) which will be discussed in Chap. 7. PIXE analysis has the advantage of a very good sensitivity and possible simultaneous detection of all heavier elements. 

Now interfacial widths can be measured by depth-profiling techniques which eg use a nuclear reaction analysis to obtain the concentration profile through a thin polymer film (108,109) or by total refiection of neutrons (110) or X-rays. However, it should be noted that neither in an experiment nor in a simulation can one ever observe the intrinsic width of an interface, which is an absolutely hypothetical object (106,111). Rather the observed width always results from a convolution of the intrinsic profile with the capillary wave broadening (106,111,112). On a lateral length scale L, one obtains for the actual mean square width... 

Another model was proposed by Lauer and co-workers [70]. These authors coated nickel phosphide-coated aluminum diskettes with 20-mm-thick DLC films by RF sputtering of graphite in methane, the same quasi-commercial procedure used by Marques. They measured the depth profile of the coatings hydrogen content by the same nuclear reaction analysis (viz. H/ N(alpha gamma)/ C) as that used by Terranova et al. [67]. Then they... 

Figure 18. Quantitative oxygen depth profiles in pure (A) and contaminated (B) molybdenum disulfide coatings. a.s recorded by nuclear reaction analysis.

Nondestructive depth profiling, which includes angle-resolved measurements, Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), peak intensity measurements from two or more peaks from the same element, and elemental intensity measurements as a function of incident electron energy (3)... 

Megaelectron volt (MeV) ion beam techniques offer a number of non-destructive analysis methods that allow to measure depth profiles of elemental concentrations in material surfaces. Elements are identified by elastic scattering, by specific nuclear reaction products or by emission of characteristic X-rays. With nuclear microprobes raster images of the material composition at the surface can be obtained. Particle-induced gamma-ray emission (PIGE) is especially suited for fluorine detection down to the ppm concentration level. 

The technical aspects of fluorine detection by nuclear reactions as well as its applications to fluorine analysis in geological and archaeological objects are reviewed. Special attention is given to the determination of exposure ages of meteorites on the Antarctic ice shield and burial durations of archaeological bones and teeth. This information can be acquired by evaluation of the shape and penetration depth of the diffusion profile of fluorine that was incorporated by the sample from the environment. For a quantitative assessment of the data, several factors like ambient conditions and diagenetic state of the material have to be taken into account. 

J.A. Sawicki, J. Roth, L.M. Howe, Thermal release of tritium implanted in graphite studied by T(d,a)n nuclear reaction depth profiling analysis, J. Nucl. Mater. 162-164 (1989) 1019... 

NDP is a prompt nuclear analysis technique, which employs a nuclear reaction that results in emission of charged particles with a specific kinetic energy. It is one of the most powerful non-destructive techniques for depth profiling of some light elements especially for and Li, which have very high thermal neutron capture cross-sections of 3837 and 940 barn respectively. 

A wide range of other nuclear reactions have been used in material science for the depth-profiling analysis of a number of different elements, some of which are tabulated by Feldman and Mayer (1986). Whether these techniques will in the future prove useful for polymers remains to be seen. 

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