Akio Ootuka

Hydrogen Content in a-SiC:H Films Prepared by Plasma Decomposition of Silane and Methane or Ethylene

The hydrogen content in a-SiC:H films prepared by the plasma decomposition of gas mixtures of silane and methane or ethylene was measured by 1H(15N, αγ)12C nuclear reaction (NR) and infrared absorption spectroscopy (IR). The contents observed by both methods can be made to agree well for most of the films by putting the average value of the inverse absorption cross section for the CHn (n=1, 2 and 3) stretching mode over all values of n as As=1.0×1021 cm-2. In some films prepared from silane and ethylene mixtures, the hydrogen content given by NR was higher than that by IR. Hydrogen release from films with a hydrogen content of over 30 atm.% was observed during NR analysis. The mechanism of the hydrogen release is discussed by comparing the IR spectra before and after ion bombardment.

Hydrogen release during erd analysis of hydrogen in amorphous carbon films prepared by rf-sputtering

Abstract The hydrogen concentration in amorphous carbon films prepared on silicon wafers by the rf-sputtering was measured by the elastic recoil detection technique (ERD) using a 12 MeV 12 C 3+ ion beam. During the measurements, it was observed that the hydrogen concentration decreased to a definite value. The decay rate and the final value of the hydrogen concentration depend on the initial amount of hydrogen and the chemical condition of carbon and hydrogen in the film. The variation in the chemical structure of the films was analysed by comparing IR absorption spectra before and after the ion bombardment. As results, it was found that dangling bonds were created by ion bombardment and that they make CC bonds with neighbors or CO bonds by capturing oxygen atoms in air.

Photon emission from resonant coherently excited heavy ions

Abstract Resonant coherent excitation and its radiative deexcitation were studied for hydrogen-like heavy ions axially channeled in a single crystal. The 6th order resonance for Ne 9+ ions along the 〈111〉 axis of a gold crystal was found at the incident energy of 88 MeV by measuring the charge state distribution after passing through the crystal. The intensity of the Ne 9+ Kα X-ray (1.02 keV) normalized to the Au M X-rays was measured for the 〈111〉-aligned and random directions of the incident beam. An enhancement in the Ne 9+ deexcitation X-rays at the resonance was detected for the first time.

Detection of Adsorbed Hydrogen on W(001) by Using 1H(15N, αγ)12C Reaction

Hydrogen coverage on W(001) was measured by using the resonant nuclear reaction 1H(15N, αγ)12C. The detection limit of the hydrogen coverage was 1/50 of the full monolayer, i.e. 4×1013 H atoms/cm2. The coverage dependence of the sticking probability of hydrogen was estimated by considering the ion-stimulated desorption of hydrogen. The zero-point energy of the vibration of adsorbed hydrogen atoms in the direction perpedicular to the surface was obtained by the Doppler broadening of the resonance width as 64±16 meV.

Detection of hydrogen adsorbed on tungsten surfaces using the 1H(15N, αγ)12C reaction

Abstract An ultratugh vacuum (UHV) system for the 1H(15N, αγ)12C reaction analysis of hydrogen adsorbed on well-defined surfaces was constructed. The detection limit of hydrogen coverage on the W(001) surface was 4 × 1013 H atoms/cm2 ( 1 50 of the full monolayer coverage). The ion-stimulated desorption process for hydrogen atoms due to the 15N ion beam was studied by measuring the decay of hydrogen coverage on W(001) at low background gas pressures, and the desorption cross section was obtained as 2.4 × 10−16 cm2. Hydrogen coverage on the W(110) surface compared with that on W(001) was estimated from the intensity profiles given by measurement of the resonance energy width.

Channeling radiation emitted from planar channeled electrons at 350 MeV in silicon crystal

Abstract Spectra of the channeling radiation emitted by 350 MeV (HO)-planar channeled electrons in silicon crystals were observed and the dechanneling length was obtained as 31 μm. A photon spectrum, only from channeled electrons, deduced from observed aligned and random photon spectra, was compared with that calculated quantum mechanically, taking account of the experimental conditions and the efficiency of the photon detector. The result showed good agreement for the absolute intensity.

Calculation of a Shadow Cone Formed by Scattering of an Ion Beam from an Atom

The shadow cone formed by the scattering of ions from an atom was calculated using Moliere potential. Calculated radii of the shadow cone by replacing the Thomas-Fermi radius, aTF with 0.85 aTF show a good agreement with an experiment for 1 keV helium ions on a titanium atom.

Radiation from axially channeled electrons at low energies

Abstract Photon energies and intensities of the radiation from axially channeled electrons have been calculated using the tight-binding approximation and a muffin-tin potential. Calculated photon energies for the Si 〈111〉 axis are systematically larger than experimental ones. Spectral line widths were calculated phenomenologically by introducing the imaginary part to the crystal potential. Results for the Si 〈111〉 axis show good agreement with experimental ones.

A double-line image of a dislocation in a silicon single crystal observed by X-ray plane wave topography

Abstract Using an asymmetric Bragg reflection, dislocation images in a silicon crystal were taken by X-ray plane wave topography with(+, −) setting. For the Si 220 reflection by Mo Kα1 radiation, the angular width of the plane wave is 0.3″. A dislocation which gives a double-line imago on a plane wave topograph was investigated. From computer simulations based on the dynamical theory of X-ray diffraction, the crystal thickness, the Burgers vector and the depth of the dislocation in the crystal were determined.

Observation of Dislocation in a Silicon Single Crystal by X-Ray Plane Wave Topography

Using an asymmetric reflection of Si 220 by Mo–Kα 1 , images of lattice defects in a nearly perfect Silicon crystal were observed by plane-wave X-ray topography with parallel ( n , - n ) setting. Notable differences between defect images in this plane-wave topograph and in the Lang traverse topograph are reported.