Electron work function - a probe for interfacial diagnosis.

A poor interface or defected interfacial segment may trigger interfacial cracking, loss of physical and mechanical functions, and eventual failure of entire material system. Here we show a novel method to diagnose local interphase boundary based on interfacial electron work function (EWF) and its gradient across the interface, which can be analyzed using a nano-Kelvin probe with atomic force microscope. It is demonstrated that a strong interface has its electron work function gradually changed across the interface, while a weaker one shows a steeper change in EWF across the interface. Both experimental and theoretical analyses show that the interfacial work function gradient is a measure of the interaction between two sides of the interface. The effectiveness of this method is demonstrated by analyzing sample metal-metal and metal-ceramic interfaces.