Chikako Takatoh

Visualizing Nanoscale Distribution of Corrosion Cells by Open-Loop Electric Potential Microscopy.

Corrosion is a traditional problem but still one of the most serious problems in industry. To reduce the huge economic loss caused by corrosion, tremendous effort has been made to understand, predict and prevent it. Corrosion phenomena are generally explained by the formation of corrosion cells at a metal-electrolyte interface. However, experimental verification of their nanoscale distribution has been a major challenge owing to the lack of a method able to visualize the local potential distribution in an electrolytic solution. In this study, we have investigated the nanoscale corrosion behavior of Cu fine wires and a duplex stainless steel by in situ imaging of local corrosion cells by open-loop electric potential microscopy (OL-EPM). For both materials, potential images obtained by OL-EPM show nanoscale contrasts, where areas of higher and lower potential correspond to anodic areas (i.e., corrosion sites) and cathodic areas, respectively. This imaging capability allows us to investigate the real-time transition of local corrosion sites even when surface structures show little change. This is particularly useful for investigating reactions under surface oxide layers or highly corrosion-resistant materials as demonstrated here. The proposed technique should be applicable to the study of other redox reactions on a battery electrode or a catalytic material. The results presented here open up such future applications of OL-EPM in nanoscale electrochemistry.

Metrologies of abrasive behaviors for understanding and upgrading CMP process

Laser scanning confocal fluorescent microscopy and the friction mode of Atomic Force Microscopy were adopted as metrologies of abrasive behaviors and removal force during polishing and cleaning processes As small as a diameter of 50nm silica particle can be individually detected and spatial distribution of particles in three dimensional space also clearly observed using the fluorescent microscopy. The fine particle removal force was able to measure using the friction mode of AFM. Accurate force was quantified by calibrating torsion spring constant of an AFM cantilever using a MEMS micro-force sensor with the particles attached to the sensor probe.