论文标题
原位高分辨率的高分辨率观察铝固态扩散纳米线：制造低于10 nm ge量子点
In-situ high resolution TEM observation of Aluminum solid-state diffusion in Germanium nanowires: fabricating sub-10 nm Ge quantum dots
论文作者
论文摘要
铝纳米线（NWS）热活化的固态反应是一个有前途的系统，因为可以在金属和半导体之间产生非常清晰且定义良好的一维触点，如果大小变得足够小，可以变成量子点。在搜索没有可变性的高性能设备的搜索中，允许确定纳米线量子点的确定性制造，避免样品变异性并在制造的点大小上获得原子量表精度，这是很高的。在本文中，我们提出了一个可靠的制造过程，以通过快速热退火（RTA）和透射电子显微镜（TEM）中的快速热退火（RTA）和原位焦耳加热技术结合使用前坐骨热退火（RTA）和原位焦耳加热技术。首先，我们提出原位直接的焦耳加热实验，以表明由于金属/NW接触附近的Al晶体和空隙形成而导致加热电极如何损坏，这可能与电迁移现象有关。我们表明，可以通过在原位加热之前包括一个额外的原位RTA步骤来保留接触质量。原位观察结果还显示了实时的交换反应是如何从Al接触板下方的几个位置同时启动的，而Al晶体逐渐在初始GE NW内逐渐生长，并沿GE（111）晶格平面呈生长界面。一旦反应前面从接触金属下方移出，两个因素危害了对Al/ge反应界面的原子准确控制。我们观察到由于透射电子显微镜中的电子束照射以及在未被激活的GE电线中的大型跳跃的出现，而在未关闭的GE电线中出现了反应界面的局部加速度，而在AL2O3中观察到了反应界面的平稳进步，其AL2O3在AL2O3中观察到了表面上的壳。仔细控制交换反应的各个方面，我们演示了一种制造过程，该工艺结合了前气和原位加热技术，以精确控制并产生轴向Al/ge/ge/al NW异质结构，而超短段则降低至8纳米。实际上，仅由显微镜分辨率限制了GE段长度的缩放。
Aluminum-germanium nanowires (NWs) thermal activated solid state reaction is a promising system as very sharp and well defined one dimensional contacts can be created between a metal and a semiconductor, that can become a quantum dot if the size becomes sufficiently small. In the search for high performance devices without variability, it is of high interest to allow deterministic fabrication of nanowire quantum dots, avoiding sample variability and obtaining atomic scale precision on the fabricated dot size. In this paper, we present a reliable fabrication process to produce sub-10 nm Ge quantum dots (QDs), using a combination of ex-situ thermal annealing via rapid thermal annealing (RTA) and in-situ Joule heating technique in a transmission electron microscope (TEM). First we present in-situ direct joule heating experiments showing how the heating electrode could be damaged due to the formation of Al crystals and voids at the vicinity of the metal/NW contact, likely related with electro-migration phenomena. We show that the contact quality can be preserved by including an additional ex-situ RTA step prior to the in-situ heating. The in-situ observations also show in real-time how the exchange reaction initiates simultaneously from several locations underneath the Al contact pad, and the Al crystal grows gradually inside the initial Ge NW with the growth interface along a Ge(111) lattice plane. Once the reaction front moves out from underneath the contact metal, two factors jeopardize an atomically accurate control of the Al/Ge reaction interface. We observed a local acceleration of the reaction interface due to the electron beam irradiation in the transmission electron microscope as well as the appearance of large jumps of the interface in unpassivated Ge wires while a smooth advancement of the reaction interface was observed in wires with an Al2O3 protecting shell on the surface. Carefully controlling all aspects of the exchange reaction, we demonstrate a fabrication process combining ex-situ and in-situ heating techniques to precisely control and produce axial Al/Ge/Al NW heterostructures with an ultra-short Ge segment down to 8 nanometers. Practically, the scaling down of Ge segment length is only limited by the microscope resolution.
