Intelligent Scanning Electrochemical Microscopy Tip and Substrate Control Utilizing Fuzzy Logic

Abstract

In this paper, we present a technique to intelligently control the motion of Scanning Electrochemical Microscopy (SECM) tip electrodes and automatically align SECM tip electrodes to the substrate with no user interaction. This intelligent method utilizes a custom fuzzy logic algorithm to control the motion of the tip electrode and automate tip/substrate alignment. The fuzzy logic control algorithm rapidly obtains SECM approach curves via a variable speed approach and automatically stops the tip electrode at a preprogrammed tip/substrate distance without “crashing” the tip electrode into the substrate. The fuzzy logic algorithm automatically adjusts the speed of the electrode based on the tip size, the enhancement of the tip current, and the distance that the tip electrode is from a user defined setpoint. We validated that both positive feedback and negative feedback approach curves obtained using the fuzzy logic algorithm matched well with simulated approach curves for both large microelectrodes (sometimes used for Surface-Interrogation SECM, a=175μm) and for conventional SECM ultramicroelectrodes (a=4.2μm). The ability to automatically stop the tip electrode is crucial for the automated sample tilt adjustment protocol. This ability allows us to automate the interactive process of (1) approaching the tip to the substrate, (2) scanning the tip across the substrate to measure the tip/substrate tilt, (3) correcting for the tip/substrate tilt. We demonstrated that this tip/substrate alignment protocol allows us to obtain highly resolved constant-height SECM images over large areas with ease.