FIM Observation of Dynamic Processes of Thin Film Growth by Vapor deposition.

利用原子分辨率高的场离子显微镜观察气相沉积金属薄膜的精细结构，研究了薄膜的生长。除了使用场蒸发观察内部结构的传统方法（方法1）之外，我们还尝试通过一种新方法（方法2）直接观察生长表面，在该方法中，在将金属气相沉积到尖端上的过程中，通过交替地打开和关闭成像电压来进行观察。方法1对钨上铜沉积的研究表明，尽管针尖温度很低（55 K），铜原子仍能从第一个撞击点在衬底表面移动约7- 9 nm，这与常规方法相反。此外，在高温针尖上沉积铜的情况下，（200- 400 K）时，入射原子在衬底表面沿入射原子动量方向运动。铜覆盖针尖热处理时再结晶的形核也发生在铜存款和钨基体的界面处。铜与铁、铬的测定结果有一定差异。在铜的情况下，没有获得单晶图像，但在钨的低折射率平面上观察到几个同心台阶环。相反，在铁和铬的情况下观察到单晶图像。沉积的薄膜区域的扩展也彼此略微不同。新方法2解决了几个基本问题，其中最重要的是成像电压对生长本身的影响。尽管有这些麻烦，一些有趣的结果已经开始出现，例如，原子在低折射率平面上的固定稍有困难，而在钨的台阶环上的固定则比较容易，等等，目前正在期待更详细的结果。

Thin film growth has been studied by observing fine structures of vapor-deposited metal thin films with a field ion microscope (FIM) well-known with its atmic resolution. In addition to the traditional method (Method 1) to observe the inside structure using field evaporation, we have attempted to directly observe the growing surface by a new method (Method 2) in which the FIM observation is performed during vapor-depositing a metal onto a tip with alternating the imaging voltage on and off. The study with Method 1 on copper deposition on tungsten, contrary to common sense, showed that copper atoms were able to move approximately 7-9nm on the substrate surface from the first hit point even though the tip temperature was very low at 55K.In addition, in the case of deposition of copper onto a high temperature tip (200-400K), the impinged atoms are found to move on the substrate surface in the direction of the momentum of the impinging atoms. The nucleation for the recrystallization under the heat treatment of a copper-covered tip was also revealed to take place at the interface of the copper deposit and the tungsten substrate. Some differences were found between the result with copper and those with iron and chromium. In the case of copper, a single crystal image was not obtained but several concentric step rings were observed on the low index planes of tungsten. On the contrarya single crystal image was observed in the case of iron and chromium. The spreading of the deposited thin film area was also slightly different to each other. With new Method 2, several fundamental problems have come to loght, most important one being the influence of the imaging voltage on the growth itself. Despite of these troubles, some interesting results have begun to come out, e.g., it is slightly hard for atoms to fix on the low index planes but easy to fix at the step rings of tungsten, and so on. More detailed results are being expected now.