Methodological Development of Large Cluster Ion Generation by Swift-Heavy-Ion-Induced Electronic Sputtering

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We previously found that large cluster ions are emitted with extraordinarily high sputtering yields in an electronic-collision-dominant velocity range. Energy distribution of these cluster ions is very narrow compared to those emitted through the linear collision cascade process in a nuclear-collision-dominant velocity range. The aim of the present study is to develop energy selected pico-to nano-ampere beams of cluster ion with any size and chemical species by applying the observed phenomena.1) The ion yield of the group Vth element emitted from III-V semiconductive chemical compounds strongly depends on the electronic stopping power because multiplicity of holes produced in the valence band plays an important role in the surface ionization process of outgoing atoms.2) It has been found first that cluster ions are produced from the III-V semiconductive chemical compounds by swift heavy ion bombardment.3) Emission yields of cluster ions containing the group Vth elements show an incident energy dependence different from those composed of the group IIIth elements only. This is because the group Vth atoms have high ionization potentials and the ionization efficiency depends so much on the multiplicity of holes which increases with increasing electronic stopping power, as shown in the group Vth ions.4) Yields of cluster ions emitted from the semiconductive chemical compounds show a power law dependence on size whose exponent is independent of incident energy.5) Beam of cluster ions can be produced by using insulating and semiconductive materials.