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

用二维位置敏感探测器对吸附有氢和/或氟原子的Si（001）晶体观察到脉冲慢速高电荷离子诱导的二次离子。根据位置和时间信息，不仅可以确定二次离子的质量和电荷，还可以确定发射的初始速度和方向。我们发现(1)F-Si键相对于表面法线倾斜20度，(2)产率与电荷态的立方成正比。由于其动能较低，所以在目前的实验条件下不会对基体造成严重的破坏，这些发现证实了慢速高电荷离子是一种很好的表面分析探针。进一步发现，慢速高电荷离子形成了(1)纳米点，每一个进入的离子形成一个纳米点，其大小与电荷状态成正比，与动能无关；(2)自组装的硫醇单层纳米管，其大小为几nm，这表明一个慢速高电荷离子溅射了几十个分子。

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.