Abstract. The fusion reactions l~ ~) 7Be and liB(p, ~) 8Be have been studied over the c.m. energy range E = 17 to 134 keV using intense proton beams and thick solid targets. In the case of liB(p, 0~) 8Be the low-energy data in terms of the astrophysical S (E) factor show an exponential enhancement (up to a factor of 1.9) due to the effects of electron screening, where the deduced screening potential is larger than expected. In the case of l~ c 0 7Be the low-energy data exhibit an enhancement by more than a factor of 200, which cannot be explained by the effects of electron screening. The enhancement arises here from the high-energy tail of an expected s-wave resonance at ER = 10 keV. The results offer an improved prospect for this reaction as advanced fuel in future fusion reactors than previously envisioned.

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Abstract. Nuclear resonant reaction analysis techniques for hydrogen depth profiling in solid materials typically have used 1 s N ion beams at 6.40 MeV and ~ 9F ion beams at 6.42 MeV, which require a tandem accelerator. We report a new technique using an ~sO ion beam at a resonance energy of 2.70 MeV, which requires only a single stage accelerator. Improved values of the nuclear parameters for the 2.70 MeV (180) and 6.40 MeV (~SN) resonances are reported. The beam energy spread was investigated for different ions and ion charge states and found to scale with the charge state. Data obtained using atomic and molecular gas targets reveal the research potential of Doppler spectroscopy. Examples of hydrogen depth profiling in solid materials using lSN and I80 ion beams are presented.

The composition and atomic depth distributions of ultrathin zirconia films (ϳ30 Å ) deposited on Si͑100͒ have been investigated using medium-energy ion scattering ͑MEIS͒. Reoxidation in 18 O 2 permits the oxygen incorporation, exchange, and mobility to be followed due to the isotope sensitivity of the MEIS technique. These quantitative studies showed that significant interfacial SiO 2 growth results when reoxidizing samples at temperatures as low as 500°C, and that this growth saturates in time and pressure but increases with temperature. Substantial isotope exchange was also observed under various experimental conditions. The results are discussed taking into account published data on the bulk and grain boundary diffusion of O in monoclinic and tetragonal zirconia, the diffusivity of O in SiO 2 , and the nanocrystallinity of the films.

HfO 2 films were grown on Si͑100͒ by chemical vapor deposition as an attempt to develop an industrially straightforward gate dielectric deposition process. During deposition at ϳ400°C the decomposition of the hafnium-tetra-tert-butoxide Hf(C 4 H 9 O) 4 precursor provides sufficient oxygen to produce a stoichiometric HfO 2 film. Medium energy ion scattering, high resolution transmission electron microscopy, atomic force microscopy, and ellipsometry were used to identify the structure and composition of the film and its interface to the Si substrate. Local crystallinity in the films increased significantly with annealing. Capacitance-voltage and current-voltage methods were used to characterize the electrical properties of simple capacitor structures. When grown on high quality ultrathin oxides or oxynitrides, the deposited films displayed very good physical and electrical properties.