Development of scanning micro-evaporator for the study of SiGeC

近年来，器件的尺寸已经缩小到纳米级，电子的介观性质变得重要起来。在这些器件中，控制界面上的电子散射当然是重要的。界面处的缺陷干扰了电子相，影响了电子在器件中的传输。在这项研究中，我们的目标是开发一种小型化的蒸发器，以便在原子平面上形成清晰的纳米结构，观察纳米结构对电子传输的影响。我们设计了一种专门用于纳米结构制作的样品夹持器。样品保持器有一个微型的STM，其上可以连接一个蒸发剂，以及一个面向STM尖端的样品。样品支架用于超高真空电子显微镜(UHV-EM)观察样品表面形成的任何纳米结构。我们使用硅单晶作为衬底，钨尖端作为蒸发剂。当针尖靠近样品表面近1 nm，并在针尖和样品之间施加几个eV的电场时，我们发现一个钨液滴从针尖一侧解吸并沉积在衬底上。这种微区沉积在硅表面制备纳米线的场蒸发技术，由于对钨尖端的场强控制不佳，不足以制备出均匀粗细的纳米线。无论如何，我们已经成功地将蒸发剂接近到接近几nm的大小的表面，这一接近过程可以用电子显微镜直接观察到。STM对蒸发剂的扫描能力使我们能够形成纳米结构，这也是通过反射电子显微镜可以观察到的。本研究表明，在原子平面和清洁的表面上进行纳米级的封装是可能的。

In recent years deivice sizes hve been decreased to nano-meter scale dimensions, and mesoscopic properties of electrons have come to be important. In these devices, it is certainly important to controle the electron scattering at the interfaces. The defects at the interface interfare the phase of the electorons and afect the electron transport in the devices. In this research we have aimed to develop a miniaturized evaporator to make a well defined nano-stuructures on atomically flat surfaces, to see any effect of the electron transport from the nano-structures.We designed a specific specimen holder for nano-structure fablication. The specimen holder has a miniaturized STM,on top of which an evaporant can be attached, and a specimen faced to the STM tip. The specimen holder is used for the ultra-high vacuum electron microscope (UHV-EM) to observe any nano-structures formed on the specimen surface.We used a silicon crystal as a substrate and a tungsten tip as an evaporant. When the tip was approached to the sample surface so close as 1 nm, and field of a few eV was applied between the tip and the sample, we found that a tungsten droplet was desorped from the tip side to be deposited on the substarte. This field evaporation technique for a micro-area deposition to produce nano-wires on the silicon surface was found to be not enough to wires of uniform thickness, because of poor controle of the field strength on the tungsten tip.Anyway, we have succeeded to approach the evaporant to a sumple surface as close as a few nm, the approaching process being observed directly by electron microscopy. The scanning capability of the evaporant by STM allow us to form nano-structures, which are also observable by reflection electron microscopy.The present reseach showed a possibility of nano-scale fablication on an atomically flat and clean surface.