Electrodeposited Gold Probe for Electrochemical Scanning Tunneling Microscopy

Abstract

Direct measurements at the solid−liquid interface on the nanometer scale provide information about various physical and chemical processes from both fundamental and applied aspects. Electrochemical scanning tunneling microscopy (EC-STM) is a powerful tool that makes it possible to perform STM measurements at the solid−liquid interfaces. However, EC-STM remains challenging due to the difficulty of fabricating the probe for tunneling current measurements in solutions. In this study, we established a novel and versatile method to easily fabricate the EC-STM probe with high reproducibility. By electrochemically depositing Au on a pyrolytic carbon formed within the glass nanopipette which has an aperture of several hundred nanometers, we achieved a sufficient insulation with almost 100% probability, which overcomes the 30-year challenge of previous EC-STM studies. High-quality EC-STM images could be stably obtained with a yield of >80% using the probe. It will pave the way for future advanced measurements at a variety of solid−liquid interfaces, such as single molecule spectroscopy and electronic structure characterizations.

In situ and ex situ approaches for molecular scale understanding of electrochemical interfaces

“…We consider that the tip deformation through local heating also occurs at 633 nm, but longer wavelength excitation is advantageous considering the higher efficiency of plasmon excitation and the wider range of appropriate conditions for self-consistent tip conditioning. We are currently conducting research to enable the above technique to achieve a high level of compatibility between EC-STM and EC-TERS, and developing various methods to control the tip size and shape, 40) and to evaluate plasmons in an electrochemical environment, 36) and models to quantitatively analyze EC-STM images. 41) As a result, it is gradually becoming possible to systematically study EC-TERS, and we expect that it will be feasible to perform experiments at the same level as the preceding UHV-TERS.…”