Correlation between electric force microscopy and scanning electron microscopy for the characterization of percolative conduction in electronic devices

The correlation betweem electric force microscopy (EFM) and scanning electron microscopy (SEM)techniques provide interpretation of the contrast features of electric force images and gave an insight into the two-dimensional (2D) electrical transport properties of RuO2-based thick film resisitors (TFRs). From the comparison between EFM. tapping mode-atomic force microscopy, SEM (secondary electrons, specimen current and X-ray energy-dispersive spectroscopy) of TFRs on the same specimen area, it turned out that the conduction mechanism was related to the grain size and to how RuO2 crystals were distributed in the glassy matrix. Dark area in EFM images corresponded to conductive-insulating interfaces. In SEM the same areas were the interfaces between the Ru=2 crystals and the insulating matrix. The 2D percolative path of the electrical current near the surface was observed in connection with the net of RuO2 grains not homogeneously dispersed in the insulating matrix.