Development of Nano-Disc electrodes for Application as Shear Force Sensitive Electrochemical Probes

Maintaining a well-defined tip-to-substrate separation is a critical area of development in scanning electrochemical microscopy (SECM). One technique that provides topographic data independently to the electrochemical measurement is shear force (SF) SECM. SF measurements are highly sensitive to factors including the tip-to-substrate separation, experimental solution, and probe geometry. We present a procedure for the fabrication of highly reproducible electrochemical probes with an active electrode disc with radii between 3 nm to 190 nm. A systematic study of the SF characteristics of these nano electrodes provides details on how to achieve the highest sensitivity and stability of SF signals, and maximize the number of SF sensitive frequencies. A new methodology to identify SF sensitive frequencies without needing to immerse the probes in solution or approach the surface is presented. Furthermore, we demonstrate that the greatest source of error in achieving reproducible SF behavior lies in the positioning of the piezo electric components and the piezo-nano electrode interface.