Electron beam lithographically-defined scanning electrochemical-atomic force microscopy probes: fabrication method...

This paper describes in detail the use of electron beam lithography (EBL) to successfully batch microfabricate combined scanning electrochemical-atomic force microscopy (SECM-AFM) probes. At present, the process produces sixty probes at a time, on a 1/4 of a three-inch wafer. Using EBL, gold triangular-shaped electrodes can be defined at the tip apex, with plasma enhanced chemical vapor deposited silicon nitride serving as an effective insulating layer, at a thickness of 75 nm. The key features of the fabrication technique and the critical steps are discussed. The capability of these probes for SECM-AFM imaging in both tapping and constant distance mode is illustrated with dual topographical-electrochemical scans over an array of closely-spaced 1 microm diameter Pt disc electrodes, held at a suitable potential to generate an electroactive species at a transport-limited rate. As highlighted herein, understanding diffusion to heterogeneous electrode surfaces, including array electrodes, is currently topical and we present preliminary data highlighting the use of SECM-AFM as a valuable tool for the investigation of diffusion and reactivity at high spatial resolution.