Fabrication and characterization of probes for combined SPM techniques based on PECVD

We describe an approach for preparing probes for combined SPM techniques, such as scanning electrochemical microscopy (SECM)/photoelectrochemical microscopy (PEM), SECM/near-field scanning optical microscopy (NSOM). The SECM/PEM probes were constructed firstly by stripping off a single mode optical fiber's polymer coating (125 μm diameter of cladding) at one end. The stripped optical fibers were then concentrically coated with Au thin film by radio frequency (RF) magnetron sputtering. The Au thin film coated optical fibers were insulating using silicon nitride thin films of low temperature plasma enhanced chemical vapor deposition (PECVD). Polishing was used to simultaneously open up the surfaces of Au ring ultramicroelectrodes (UMEs) of SECM and the apertures of PEM. Once fabricated, the probes were characterized with excellent adhesion qualities at the interfaces of Au thin film/optical fiber and silicon nitride thin film/Au thin film by scanning electron microscopy (SEM) measurement. The silicon nitride thin films were found to be free of microcracks by SEM. Electrochemical properties of the probes were investigated by cyclic voltammetry (CV) through three-electrode system. The electrochemical responses of the probes are sigmoidal in shape at different scan rates and indicate that the fabricated Au ring electrodes exhibit UMEs' electrochemical response.