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

The correlation between electron force microscopy (EFM) and SEM techniques provided interpretation of the contrast features of electron force images and gave an insight into the two-dimensional (2D) electron transport properties of RuO2-based thick film resistors (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, the conduction mechanism was related to the grain size and to how RuO2 crystals were distributed in the glassy matrix. Dark areas in EFM images corresponded to conductive-insulating interfaces. In SEM the same areas were the interfaces between the RuO2 crystals and the insulating matrix. The 2-dimensional percolative path of the electron current near the surface was observed in connection with the net of RuO2 grains not homogeneously dispersed in the insulating matrix.