Cathodic electropaint insulated tips for electrochemical scanning tunneling microscopy.

A method of preparing tungsten tips insulated for in situ scanning tunneling microscopy (STM) work is presented. Tips were electrocoated at low applied voltages using an organic solution of the cathodic electropaint rather than the more frequently utilized electropaint emulsions. The insulated tips were then characterized using cyclic voltammetry and electrochemical STM (EC-STM). They displayed low Faradaic leakage currents under electrochemical conditions and provided for high-resolution STM imaging in electrolyte solution. Flat terraces on a monocrystalline Au surface and adlayers of 5,10,15,20-tetraphenyl-21H,23H-porphine cobalt(II) were imaged under potential control in dilute HClO4 using the fabricated tips, and atomic or molecular resolution images were obtained in both cases. The developed procedure allows for the fast, reproducible generation of large numbers of electrically insulated tungsten tips suitable for EC-STM imaging experiments.