M. Bruneaux

Nuclear microanalysis using MeV carbon ion backscattering usefulness and applications.

The amplitude-energy relationships for surface barrier detectors were measured for4He and12C particles, as well as the corresponding energy resolutions. It is shown that the use of12C beams presents no marked advantage for increasing mass or depth resolution. On the other hand pile-up phenomena are drastically reduced by using12C backscattering. Applications are shown to the determination of trace amounts of Sb or Yb near the surface of iron. Gold contaminations of silicon surfaces were precisely measured within minutes down to 5·1011 gold atom/cm2, the limiting sensitivity being of the order of 1010 atom/cm2 for traces of heavy elements, such as Au, Hg, Pb, etc. Sensitivities for lighter elements are discussed.

Oscillating trajectories in planar channeling studied by backscattering from iron crystals

Abstract Backscattering experiments with 1.9 MeV helium ions were performed to study the oscillating trajectories of particles in planar channels of iron crystals. Strong maxima in the planar aligned spectra were observed. A stochastic model yields a good fit to the experimental results.

AXIAL AND PLANAR CHANNELING PHENOMENA IN QUARTZ.

Abstract Axial channeling along the [00.1] c-axis and the [2λ.0] A 2-axis of α-quartz as well as planar channeling along planes containing one of these two axes were studied. The effects of silicon and oxygen sublattices were separated by using backscattering for the silicon sublattice and the nuclear reactioq O16(d,p)O17∗ for the oxygen sublattice. Experiments were carried out with H+, D+ and He4 + in the 0.5 MeV to 2 MeV range. Results represented using well chosen reduced coordinates follow single laws satisfactorily. For axial channeling the full width at half minimum l1/2 of the surface extinction curves depends on √Z 1 Z 2/Ed. For the channeled fraction the reduced depth is xp 2dZ 1/E,p 2 corresponding, even for the silicon sublattice. to the thermal vibrations of the oxygen atoms. The results obtained for the minimum yields are in good agreement with those calculated. The depth dependence of l 1/2 shown. A rather weak effect is observed for silicon planes (not larger than 50 per cent). For the oxyg...

Complementary use of microanalysis by the direct observation of nuclear reactions and of backscattering induced by charged particles

Techniques are described which combine the use of nuclear reactions and of backscattering to obtain analytical results which would be difficult or impossible to reach using one of these methods only. The principles of stoichiometry determination by plateau height analysis are developed both for backscattering and for narrow resonances of nuclear reactions. Examples of applications are given to the determination of the composition of various thin films of aluminium and silicon oxides, silicon nitrides and calcium fluorides. The analysis of samples smaller than the beam, using backscattered particle monitoring, is presented.

Search for internal oxidation in rare earth-implanted iron☆

Abstract The possibility of “internal oxidation” in Yb-implanted iron is studied via 18 O tracing experiments. For a 400 keV Yb-implantation in iron single crystals, no oxygen diffusion occurs at the Yb depth under implantation or annealing up to 520°C.

Study of atomic displacements in He+ irradiated silicon and a silicon-germanium alloy, through rutherford scattering

Abstract The disorder created by He+ ions of 275 keV and 1610 keV in Si and in a Si-Ge alloy (0.6 per cent atomic Ge) has been studied at 295 and 85°K through the use of channeling and back scattering of these ions. The disorder is measured through the relative yield of back-scatter for the beam incident in and directions. In both crystals, the disorder is not linear with fluence, and shows a tendency to saturate. In many cases the disorder measured along channels is larger than along channels, which indicates a prevalence of ‘interstitial-type’ defects. However, there is no indication of the structure of the defects. Part of the disorder could be attributed to slight displacements of atoms in the strain field of radiation defects. The low temperature irradiations create more disorder than room temperature irradiations, and this excess disorder does not fully anneal at 120°C. In Si(Ge), the number of Si or Ge scatterers is close to the concentration ratio even at high fluences. Thi...

Temper embrittlement and intergranular segregation of antimony: A quantitative analysis performed with the backscattering of energetic ions

The intergranular segregation of antimony associated with temper embrittlement in a low carbon manganese steel was quantitatively studied through the backscattering of MeV12C12+ and1214N12+ ions. The principles of the technique and its application to interface segregation problems are briefly explained and its main advantages discussed. The influence of various heat treatments was investigated and shown to strongly influence the segregation taking place in the α field. Segregation could not be detected in the γ field. The kinetics of the phenomenon in the critical range (400° to 600°C) is described. The role of the micro-structure was studied and it is shown that segregation does not occur only at the previous austenitic grain boundaries but at all the disordered high angle boundaries of the structure. The grain boundary Sb content after a reversion and a resegregation treatment was also studied. The results are interpreted in terms of a reversible type of segregation taking place entirely in the α phase.