Fabrication of Probes for In-situ Mapping of Electrocatalytic Activity at the Nanoscale

Abstract

Scanning electrochemical microscopy (SECM) is well established as a powerful means to spatially map the electrochemical activity of materials. By scanning a microelectrode probe over a surface immersed in an electrolyte solution, spatially resolved information about surface activity can be gained through the measurement of local electrochemical processes. The combination of SECM with atomic force microscopy (SECM-AFM) has been identified as an elegant means to take the resolution of such measurements down to the nanoscale. The integration of an addressable electrode onto dual function scanning force probes is advantageous not only because of the small electrode dimensions, but moreover because this permits scanning at constant tip-surface separation using the AFM cantilever optical feedback. Thus, topographical features can be easily measured and deconvoluted from activity variations, and short working distances can be achieved.In this work we present two novel approaches to the fabrication of probes for SECM-AFM. One method involves the modification of commercially available metallic needle electric force microscopy (EFM) probes to yield high-aspect ratio coated needle probes with an addressable nanodisk electrode at the apex. The second approach involves a focused ion beam (FIB) milling procedure to integrate a platinum electrode into commercial silicon nitride AFM probes. The former approach is found to be more successful and the imaging capability of these probes is demonstrated using a gold-on-silicon patterned substrate.