Miyazawa K, Izumi H, Watanabe-Nakayama T, Asakawa H, Fukuma T
Division of Electrical Engineering and Computer Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
Nanotechnology. 2015 Mar 13;26(10):105707. doi: 10.1088/0957-4484/26/10/105707. Epub 2015 Feb 20.
Recently, possibilities of improving operation speed and force sensitivity in atomic-scale atomic force microscopy (AFM) in liquid using a small cantilever with an electron beam deposited (EBD) tip have been intensively explored. However, the structure and properties of an EBD tip suitable for such an application have not been well-understood and hence its fabrication process has not been established. In this study, we perform atomic-scale AFM measurements with a small cantilever and clarify two major problems: contaminations from a cantilever and tip surface, and insufficient mechanical strength of an EBD tip having a high aspect ratio. To solve these problems, here we propose a fabrication process of an EBD tip, where we attach a 2 μm silica bead at the cantilever end and fabricate a 500-700 nm EBD tip on the bead. The bead height ensures sufficient cantilever-sample distance and enables to suppress long-range interaction between them even with a short EBD tip having high mechanical strength. After the tip fabrication, we coat the whole cantilever and tip surface with Si (30 nm) to prevent the generation of contamination. We perform atomic-scale AFM imaging and hydration force measurements at a mica-water interface using the fabricated tip and demonstrate its applicability to such an atomic-scale application. With a repeated use of the proposed process, we can reuse a small cantilever for atomic-scale measurements for several times. Therefore, the proposed method solves the two major problems and enables the practical use of a small cantilever in atomic-scale studies on various solid-liquid interfacial phenomena.
最近，人们对使用带有电子束沉积（EBD）尖端的小悬臂在液体中提高原子尺度原子力显微镜（AFM）的操作速度和力灵敏度的可能性进行了深入探索。然而，适用于这种应用的EBD尖端的结构和特性尚未得到很好的理解，因此其制造工艺也尚未确立。在本研究中，我们使用小悬臂进行原子尺度的AFM测量，并阐明了两个主要问题：悬臂和尖端表面的污染，以及具有高纵横比的EBD尖端的机械强度不足。为了解决这些问题，我们在此提出一种EBD尖端的制造工艺，即在悬臂末端附着一个2μm的二氧化硅珠，并在该珠上制造一个500 - 700nm的EBD尖端。珠的高度确保了足够的悬臂 - 样品间距，即使使用具有高机械强度的短EBD尖端，也能抑制它们之间的长程相互作用。在制造完尖端后，我们用Si（30nm）覆盖整个悬臂和尖端表面，以防止污染的产生。我们使用制造的尖端在云母 - 水界面进行原子尺度的AFM成像和水化力测量，并证明了其在这种原子尺度应用中的适用性。通过重复使用所提出的工艺，我们可以多次重复使用小悬臂进行原子尺度测量。因此，所提出的方法解决了两个主要问题，并使小悬臂能够实际应用于各种固 - 液界面现象的原子尺度研究。
