K. Komaki

PLASMA OSCILLATIONS EXCITED BY A FAST ELECTRON IN A METALLIC PARTICLE.

The interactions between a fast incident electron and a metallic spherical particle full of a free electron gas as the conduction electrons are studied using the hydrodynamic equations of Bloch. The obtained energy spectrum of a transmitted electron is composed of the well known peak due to the bulk plasma oscillations with small corrections and the peak due to the surface plasma oscillations which are given by sum of various modes of oscillations with different energies. The energy value of the surface oscillations at maximum intensity increases with increasing particle size and tends to that in the foil case. Numerical examples are given for aluminum particle coated with aluminum oxide and for colloidal alkali metal in alkali halide. The latter example is compared with experimental observations. The possibility of the plasma radiation is also discussed. The radiated photon energy is the same as that in the Mie scattering from small particle. Energy spectrum, angular distribution and photon yield are num...

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.

Quantized rosette motion of energetic electron around an atomic row in crystal

Abstract Wave functions of energetic electrons bound by an atomic row in a crystal and excitation probability of each level are calculated. Results are in good agreement with experimental ones.

Resonant coherent excitation of 390 MeV/u Ar ions planar channeled in Si crystals

Resonant coherent excitation of the 1s electron to na 2 states in a hydrogen-like ion was studied through measurements of the survived fraction of 390 MeV/u Ar 17a planar channeled in a Si crystal. Adopting a totally depleted Si surface barrier detector as a target crystal, the charge state of the individual emerged ion was measured in coincidence with the energy deposition in the target. By changing the incident direction along theO2 20 U ,O 004 U, andO1 11 Uplanes, a series of clear resonances were observed as the decrease in the survived charge fraction due to higher electron loss probability for the excited state. Each resonance profile reflects energy splitting of the na 2 manifold originated from l‐ s interaction and Stark eAect due to the crystal field. From the correlation between the energy loss and survived charge fraction, transition energy as a function of the ion trajectory amplitude is deduced which is in good agreement with calculated results. ” 1998 Elsevier Science B.V. All rights reserved.

Potential sputtering of proton from hydrogen-terminated Si(100) surfaces induced with slow highly charged ions

A potential sputtering mechanism of hydrogen has been studied for impact of slow highly charged Xeq+ ions (<5 keV, q=4–12) on well-defined H-terminated Si(100) surfaces. It was found that the sputtering yields of protons are proportional to qγ (γ∼5), independent of the surface condition, that is, for both Si(100)2×1-H surface and Si(100)1×1-H surface. The yield for Si(100)1×1-H surface was ten times larger than that for Si(100)2×1-H surface, although the H coverage of the former is only twice the latter. Surface roughness is found to be the key parameter to vary the yield, and also to influence the energy distribution of sputtered protons. These findings are consistently explained with a pair-wise bond-breaking model induced by a double electron capture, where the classical over barrier process plays an essential role.

Strong charge state dependence of H+ and H2+ sputtering induced by slow highly charged ions

Abstract Secondary ion emission has been studied for very slow (∼ 0.01 νB) highly charged Ar and N ions bombarding C60 containing hydrogen as an impurity. It is found that the fragmentations of C60 are very rare even for Ar16+ bombardments. On the other hand, the sputtering of H+ and H2+ has been observed to increase drastically as a function of incident charge q like qγ (e.g., γ ∼ 4.6 for H+ sputtering by 500 eV Arq+).

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.

Angular distribution of X-ray emission from resonant coherently excited highly-charged heavy ions

Abstract X-rays emitted from resonant coherently excited (RCE) n =2 states of 390 MeV/amu hydrogen-like Ar 17+ ions were observed under planar channeling in a Si crystal. The resonance profiles for X-ray emission consisting of two peaks for j =1/2 and j =3/2 are characterized by suppression of the j =1/2 peak. The degeneracy of the n =2 states are removed by Stark effect due to the static crystal field. The RCE probability of these Stark splitted substates differs, reflecting the polarization of the oscillating crystal field. However, the associated alignment was not clearly observed. It is explained by the fact that both polarization of the oscillating crystal field and the wave functions of Stark-mixed n =2 states depend on the distance from the channel center, and the X-ray emission is preferred in a channel center in a crystal.

De-excitation X-rays from resonant coherently excited 390 MeV/u hydrogen-like Ar ions

Resonant coherent excitation (RCE) of 390 MeV/u hydrogen-like Ar{sup 17+} ions planar channeled in a Si crystal was investigated through measurements of the de-excitation X-rays as we11 as the charge state distribution of the transmitted ions. We observed enhancements of both the fraction of ionized Ar{sup 18+} ions and the intensity of the de-excitation X-rays under the RCE condition. The n=2 states of Ar{sup 17+} in the crystal are split into four energy levels due to spin-orbit interaction and Stark effect induced by the planar potential of the crystal. The intensities of the X-rays from the lower two levels were found to be smaller compared with those from the higher two levels, which is explained by the dominance of the 2s component not decaying via a single photon emission. The difference between the resonance profiles of the charge state and the X-ray reflects the nature of n=2 states in the crystal field.