Macro- and Micro Kelvin Probe in Tribological Studies

Abstract

The Kelvin method of electronic work function (EWF) measurement of contact potential difference (CPD) technique is an excellent non-destructive monitoring technique. Lord Kelvin offered the CPD in 1898. The CPD technique was developed considerably parallel with quantum theory of solids. As researchers were trying to correlate experimental data with theory, the EWF was explained according to the fundamental quantum mechanical parameters of solids. However, a strong influence of surface conditions on the experimental results was found and the technique was practically forgotten. Later, problems in the measurement of surface conditions have gained a special importance with the development of solid-state electronics. However, systems of surface analysis began to appear during the same years. Such systems were complicated devices attached to ultrahigh vacuum systems. These systems have overshadowed the CPD technique. An analysis of published papers has shown that surface analysis systems yield interesting results when conducting fundamental experiments with pure model surfaces. Results are not reliable for most of engineering surfaces. It is explained that surface analysis systems, in most cases, do not analyse the surface, but instead analyse artefacts on the surface. According to our experience, CPD does give reliable information about the surface.