Study of the contrast in electric force microscopy images of RuO2-based thick-film resistors

The contrast mechanism of electric force microscopy (EFM) operating in stat ic and dynamic modes have been investigated and applied to the clarificatio n of the electrical conduction properties of RuO2-based thick-film resistor s. Both the magnetic and the electrical contributions to the overall EFM si gnal and the corresponding contrast have been analysed and compared by usin g different types of atomic force microscopy tip (with a magnetic coating a nd with a Pt/Ir coating). It has been found that the EFM contrast changes o n inverting the voltage polarity of the samples. The regions surrounding th e RuO2 grains present an EFM signal which is lower for a negative bias than for a positive bias at low values of the applied voltage; this signal diff erence tends to disappear on increasing the absolute bias value. This behav iour, typical of semiconductors, ascribes to the above regions semiconducti ng properties.