Batch Fabrication of AFM-Tip Integrated Disk Nanoelectrodes

Abstract

Ultramicroelectrodes (UME) integrated into atomic force microscopy (AFM) probes have been fabricated for combining Atomic Force Microscopy with Scanning Electrochemical Microscopy (AFM-SECM). Typically, frame-electrodes with dimensions of 500 nm - 900 nm are integrated at a defined distance above the apex of pyramidal AFM tips by modifying commercially available cantilevers with a conductive layer and an insulating layer, and consecutively exposing the electrode area by three-dimensional focused ion beam (FIB) milling. These combined AFM-SECM probes allow simultaneously recording topographical and electrochemical information on a variety of samples ranging from biological specimen to electrode materials. This contribution presents the integration of disk-typed electrodes with diameters of 50 nm – 100 nm diameter, mainly based on batch fabrication processes. Hence, the cost and time of fabrication can be significantly reduced, and secondly, reducing the electrode size improves the lateral resolution achievable in SECM experiments. Basically, the cantilevers are microfabricated from low-stress silicon nitride deposited onto a Si (100) wafer. Then, pyramidal tips combined with ultramicroelectrodes are formed by simultaneously patterning conductive layer at the substrate. After insulation of the conductive layer with a thin layer of silicon nitride, the cantilever array is transferred to Pyrex glass by anodic bonding at optimized conditions, and alkali potassium hydroxide bulk silicon etching was applied for releasing the cantilever array. First images recorded with AFM tip-integrated disk-shaped electrodes will be presented on simultaneously imaging topographical and electrochemical information at polymer membranes.