In-Situ Spectroscopy of Ion-Induced Photon Emission During Metal Nanoparticle Formation in Silica Glass with High-Flux C
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remain inside the substrate. The sputtered atoms and ions may create a plasma in front of the surface, which either changes the surrounding electric potential or increases the collision probability with the incident ions[4]. It has been suggested that dynamic beam-surface interactions influence not only ion beam transport but also intra-solid processes of particle morphology including the in-plane arrangement, particularly within a few tens nanometers beneath the surface. Accordingly, in-situ spectroscopy of ion-induced photon emission is applied to investigate dynamic effects of beam-surface interactions, primarily of sputtering effects at the sample surface and in the vicinity. Needless to say, the optical technique has an advantage of non-invasive detection and provides direct information on kinetics of sputtered and reflected particles from the solid. Although there have been many reports on ion-induced photon emission in a visible region conducted with light ion beam such as D', He', Ar÷ [5,6,7]. Most of them have used positive ions and have aimed at development of ion-beam-analysis methods or research on beam-solid interactions of plasma-facing materials for nuclear fusion reactors. There are few reports on photon emission induced by negative heavy ions, with either metals or insulators, since negative-ion technology has just recently become available for various material applications[8]. The charging-free advantage of negative ions leads to an electric potential near the surface different from those of positive ions. Negative ions may give different sputtering processes, either via charged states of sputtered ions or via the surrounding potential. Extensive research on beam-solid interactions of negative ions is demanded to establish the high-flux implantation technology. The purpose of the present experiment is to understand processes of sputtering and other beam-surface interactions by using optical spectroscopy and eventually to obtain systematic understandings of the high-flux implantation process. 191 Mat. Res. Soc. Symp. Proc. Vol. 569 01999 Materials Research Society
EXPERIMENTAL PROCEDURES A plasma-sputter-type ion source provided negative Cu ions of 60 keV with current density ranging from 30 VA/cm2 up to 100 WA/cm 2 . The irradiation time was varied from 160 sec to 50 sec, corresponding to a total dose of 3 x10 16 ions/cm 2. Substrates used were silica glasses (OH- < 200 ppm) of 15 mm in diameter and 0.5 mm thick. The beam current was measured in immediate front of the substrate by a Faraday cup with 40 mmý in diameter. Although an electron suppressor is usually placed on the sample stage to confirm the beam current, the suppressor is removed to Vu eliminate an EDX background and to "Dvamber attain a sufficient solid angle for light emission into the detector.
Fig. 1 shows a block diagram
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of the experimental setup. A Mo mask sourof a 12 mm(P-aperture is used to ensure 6OkeV the thermal contact to the sample stage and to dissipate a beam load onto the sample. A spectroscopic system
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