Resonant nuclear reaction profiles

Kalbitzer and his colleagues used the Si (p, y) resonant nuclear reaction to profile the range distribution of 10-MeV Si implanted into Ge. Figure 8 shows their experimental results (data points), along with theoretical predictions (curves) of what is expected. 

NRA is a powerful method of obtaining concentration versus depth profiles of labelled polymer chains in films up to several microns thick with a spatial resolution of down to a few nanometres. This involves the detection of gamma rays produced by irradiation by energetic ions to induce a resonant nuclear reaction at various depths in the sample. In order to avoid permanent radioactivity in the specimen, the energy of the projectile is maintained at a relatively low value. Due to the large coulomb barrier around heavy nuclei, only light nuclei may be easily identified (atomic mass < 30). 

A widely used technique for depth profiling hydrogen (in this case the H isotope) uses resonant nuclear reactions (Lanford et al., 1976 Ziegler et al., 1978 Clark et al., 1978), i.e., the reaction... 

A technique which can yield hydrogen concentration profiles of a glass surface(19) without the complications of ion milling involves using the resonant nuclear reaction between hydrogen 1H) and (1 N). At precisely 6.385 M V (lab) there is a resonance in the reaction 3N + H = X +... 

One technique that has been able to measure hydrogen concentration in a thin film and do a depth profile, without reliance on standards, uses a resonant nuclear reaction technique.16 In this procedure, the nuclear reaction between a hydrogen atom ( H) and an energetic nitrogen-15 atom (1SN) is used. That is... 

M. Kregar, J. Muller, P. Rupnik, F. Spiler, Concentration profile measurements using multiply resonant nuclear reactions, Fizika 9 (1977) 81. 

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. 

Fig. 10. Hydrogen depth profiles obtained from the resonant nuclear reaction of an as-deposited a-Si H film and after laser annealing at different intensities. [After Thomas et al.

An important advance in understanding in detail the role of hydrogen during hydrolysis has been the use of ion-beam techniques, and particularly resonant nuclear reactions (RNR), which allow direct depth profiling of important elements such as H, Na, Al, and O. For instance, using RNR, Petit et al. (1987) and Schott and Petit (1987) have shown for the first time that pyroxene, olivine, and feldspar surfaces become protonated and/or hydrated to depths of several hundred angstroms during hydrolysis. 

Petit, J. C., G. Della Mea, J, C. Dran, J. Schott, and R. A. Berner, (1987), Diopside Dissolution New Evidence from H-Depth Profiling with a Resonant Nuclear Reaction, Nature 325, 705-706. 

Tables 1 and 2 show some of the recently used non-resonant and resonant nuclear reactions, respectively. In general these reactions are used to depth profile the element of interest but can also be used to determine the concentration of a particular element in a sample. The following sections describe some of the many applications of NRA and ERD.

Ion implantation of materials, to change its properties, has many important applications in materials science and semiconductor technology. Several non-resonant and resonant nuclear reactions have been used for the profiling of such implantations. The 0.992 MeV resonance of the Al(p,y) Si resonant nuclear reaction has, for example, been used to profile the thermal diffusion of aluminum in aluminum-implanted stainless steel when heated to temperatures of between 450°C and 650°C. 

In the analysis of light elements by PIGE, the reactions by Coulomb excitation (p, p y) are common. The resonance nuclear reactions (p, y), (p, ay) are used occasionally for the depth-profile. 

Chemical diffusion of Ti under anhydrous conditions at latm and under fluid-present elevated pressures (1.1 to 1.2GPa) conditions was measured in natural zircon. Nuclear reaction analysis and the resonant nuclear reaction 48xi(p,Y)49y were used to measure diffusion profiles. The Arrhenius expression for diffusion at 1350 to 1550C and latm was ... 

This method is of course restricted to nuclei which provide a satisfactory resonance, usually with a (p,Y) or (p,a) reaction. These are most often found in the region of elements between Z = 10 and Z = 28, although a few examples exist for lighter elements. Unfortunately above Ni there are no nuclear reaction techniques which have proved satisfactory for profiling purposes. 

B. Maurel, G. Amsel, J.P. Nadai, Depth profiling with narrow resonances of nuclear reactions theory and experimental use, Nucl. Instr. Meth. 197 (1982) 1-13. 

G. Amsel, B. Maurel, High resolution techniques for nuclear reaction narrow resonance width measurements and for shallow depth profiling, Nucl. Instr. Meth. 218 (1983) 183-196. 

Due to the complexity of nuclear forces, predictions from nuclear model calculations for the cross sections of nuclear reactions and their dependence on energy and detection angle are difficult, and even if it is possible, they are not precise enough for analytical purposes. Thus, one has to rely on measured data. There are many published experimental cross-section data in the basic literature on nuclear physics, but usually the same problem occurs again neither are the experimental conditions the same, nor are the precisions good enough for NRA. For depth profile measurements, the knowledge of precise resonance parameters is crucial, and often the published experimental data have to be remeasured to fulfill the requirements of the technique. 

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