Damage free and high sensitive elemental analysis of adsorbed atoms with slow highly charged ions

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Secondary ions induced with pulsed slow highly charged ions have been observed with a two-dimensional position sensitive detector for a Si(001) crystal adsorbed with hydrogen and/or fluorine atoms. From the position and timing information, not only the mass and charge of the secondary ions, but also the initial velocity and direction of emission have been determined. We found that (1)the F-Si bond is tilted 20 degree with respect to the surface normal, and (2) the yield is proportional to the charge state cubed. Because the kinetic energy is low and so does not cause serious damage on the substrate in the present experimental condition, these findings confirm that slow highly charged ions is an excellent probe of surface analysis. It was further found that slow highly charged ions form (1) nanodots, one dot for each incoming ion, the size of which is proportional to the charge state, and independent of the kinetic energy, and (2) nanocrators for a self-assembled monolayer of thiol with a size of several nm, which indiates that several tens of molecules are sputtered with one slow highly charged ions.