Scanning Contact Force Microscope-Scanning Electrochemical Microscopy: A New Approach for Tip Positioning and Simultaneous Imaging of Interfacial Topography and Activity

Scanning Electrochemical Microscopy (SECM) offers exceptional spatial and temporal resolution while enabling the detection of localized chemical activity. However, the conventional SECM methodology lacks a robust positioning mechanism, leading to the convolution of electrochemical responses with topographical features. This study presents an innovative SECM positioning feedback mechanism, termed as "Scanning Contact Force Microscopy (SCFM)", leveraging microforce servo control principles to precisely determine the "contact zero point" between the tip and the substrate. The core innovation lies in the integration of a low-stiffness, flexible microbeam with a high-precision capacitive displacement sensor (CDS), significantly minimizing the contact force exerted on the tip. Experimental results demonstrate that SCFM exhibits a normal positioning accuracy of less than 8 nm and a contact force below 20 mu N. Morphology detection errors relative to commercial AFM systems were under 2%. Through the integration with SECM, the electrochemical signal is decoupled from the morphology of glassy carbon (GC) substrate with complex structure. Fully compatible with laser-pulled SECM glass electrodes, this technique requires no modifications to electrodes or instrumentation, offering a simple, cost-effective, and versatile solution for advancing nanoscale electrochemical investigations.