Mesurement of Passive Film Growth and Breakdown, and Excitation of Local Phenomena on Electrode By Using Electrochemical AFM・STM

本研究将原位电化学AFM/STM技术应用于钝化金属表面，为分析钝化膜的形成、生长和击穿等电极过程提供有价值的信息。并对电极的局部电化学过程进行了微改性和激发。(1)利用原位电化学原子力显微镜对溅射在石英玻璃、钛板电极和铝电极上的钛膜电极在极化条件下的生长和击穿过程进行了观察。对于钛薄膜，在薄膜生长过程中由于很高的电场进行了微晶化，导致了氧化层表面的粗糙，称为钝化膜的击穿。(2)利用电化学隧道光谱技术研究了Fe和Ti上形成的钝化膜的电学性质。研究了电化学体系中隧道势垒形状与电位扫描的关系，以及尖端电极通过半导体电极中的空间电荷层对极化条件的影响。(3)用原子力显微镜观察了碳钢在活化溶解过程中表面形态的变化，并与扫描电子显微镜和强制激光显微镜的图像进行了比较。针对碳钢中的珠光体组织，讨论了腐蚀过程。(4)利用原子力显微镜针尖实现了阳极氧化膜生长后对铝表面的微改性。然而，经过改进后，针尖被机械破坏，导致观察到的AFM图像退化。为此，需要开发更复杂的改进技术。

In this research in-situ electrochemical AFM/STM technique was applied to passivated metal surface to obtain valuable information for analysis of electrode process such as passive film formation and growth, and breakdown. Micro-modification and excitation of local electrochemical process on electrodes were also aimed. (1) In-situ electrochemical AFM was applied to Ti film electrode sputtered onto quartz glass, Ti plate electrode, and Al electrode to observe growth and breakdown processes of the passive film under polarization condition. For Ti film proceeding of micro-crystallization due to very high electric field during film growth was found, resulting in surface roughening of the oxide surface, known as breakdown of the passive film. (2) Electrochemical tunneling spectroscopy technique was applied to the passive films formed on Fe and Ti to investigate their electronic properties. Tunneling barrier shape as a function of potential scanning in the electrochemical system, and effect of tip electrode on polarization condition through the space charge layr in the semiconductive electrode were evaluated. (3) Morphological change of corbon steel surface during active dissolution was observed by AFM.Results were compared with images obtained by SEM and conforcal laser microscopy. Corroding process was discussed concerning with the pearlite structure in the carbon steel. (4) AFM tip was used to achieve micro-modification of Al surface after anodic oxide film growth. After modification, however, tip was mechanically damaged resulting in degradation of AFM image observed. For such purpose development of more sophisticated technique for modification is required.