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

用以大气分辨率著称的场离子显微镜(FIM)观察了气相沉积金属薄膜的精细结构，研究了薄膜的生长。除了传统的用场蒸发观察内部结构的方法(方法1)外，我们还尝试用一种新的方法(方法2)直接观察生长表面，其中FIM观察是在气相沉积金属到针尖上的过程中通过改变成像电压开和关来进行的。方法1对钨上沉积铜的研究与常识相反，结果表明，即使在55K温度很低的情况下，铜原子仍能从第一个撞击点在衬底表面移动约7-9 nm。此外，在将铜沉积到高温尖端(200-400K)的情况下，被撞击的原子在衬底表面上沿着撞击原子的动量方向移动。镀铜尖端热处理时的再结晶形核也发生在铜层与钨衬底的界面处。铜的测定结果与铁、铬的测定结果有一定的差异。在铜的情况下，没有得到单晶图像，但在钨的低折射率平面上观察到了几个同心阶梯环。反之，在铁和铬的情况下，观察到了单晶图像。沉积薄膜面积的分布也略有不同。在新方法2中，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。尽管有这些问题，但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固定略有困难，但在钨的台阶环上很容易固定，等等。现在预计会有更详细的结果。

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.