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

用二维位置灵敏探测器对吸附有氢和/或氟原子的Si（001）晶体进行了脉冲慢高电荷态离子诱导二次离子的观测。从位置和定时信息中，不仅确定了二次离子的质量和电荷，而且还确定了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）产额与电荷态的立方成正比。由于动能低，因此在本实验条件下不会对基底造成严重损伤，这些发现证实了慢高电荷离子是表面分析的优良探针。进一步发现，缓慢的高电荷离子形成（1）纳米点，每个进入的离子一个点，其大小与电荷状态成比例，并且与动能无关，以及（2）纳米粒子，用于具有几nm大小的硫醇自组装单层，这表明几十个分子被一个缓慢的高电荷离子溅射。

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.