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

Abstract

The contrast mechanism of electric force microscopy (EFM) operating in static and dynamic modes have been investigated and applied to the clarification of the electrical conduction properties of RuO₂-based thick-film resistors. Both the magnetic and the electrical contributions to the overall EFM signal and the corresponding contrast have been analysed and compared by using different types of atomic force microscopy tip (with a magnetic coating and with a Pt/Ir coating). It has been found that the EFM contrast changes on inverting the voltage polarity of the samples. The regions surrounding the 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 difference tends to disappear on increasing the absolute bias value. This behaviour, typical of semiconductors, ascribes to the above regions semiconducting properties.