Characterization of localized electrochemical properties of Si₃N₄-TiC ceramic nanocomposite using dual-electrode scanning probes

Scanning probe microscopy, having the capability of nano-positioning and nanomanipulation, enables the characterization of material properties at a very small scale. In our previous work, the investigation of localized electrochemical reactions in Si₃N₄-TiC ceramic nanocomposites had been demonstrated using a single conductive scanning probe in a scanning impedance microscope (SIM). The results have provided experimental evidence that links the relations among microstructural heterogeneity, electrochemical property, and sintering behavior of spark plasma sintered ceramics. This single-probe SIM measurement gave through-body electrochemical information of specific surface feature of interest; however, the characterization of across-surface material properties in nanoscale is still much desired and unavailable. To further investigate the heterogeneity of materials, we have designed and developed a dual-electrode scanning probe (DESP), which is capable of localized electrochemical characterization across the surface of a material. These probes were designed based on computer simulation and iterations, and fabricated using common semiconductor processing techniques. The span of two probes (electrodes) in our first prototypes was 10∼15 microns, which can be further reduced with optimized parameters. The DESP probes have been evaluated on Si3N4-TiC nanocomposites to demonstrate their functionality in topography scanning and in-situ impedance measurement. The impedance spectroscopy revealed two distinct impedance patterns for measurements across TiC-rich and Si₃N₄-rich surface regions. The design, fabrication, and evaluation of DESP were discussed in addition to the analysis of Si₃N₄-TiC nanocomposites.