Invisible high workfunction materials on heterogeneous surfaces

We demonstrate that the determination of workfunction of heterogeneous surfaces by electron spectroscopy measurements is complex due to enhanced secondary electron emission from the lower workfunction material. This can lead to misunderstanding the electronic properties of interfaces in electronic devices and have significant influence on the design and performance of the interfaces therein. Ultraviolet photoelectron spectroscopy (UPS) measurement on a range of artificially created ITO-Au heterogeneous surfaces demonstrates that contributions to the secondary electron cut-off are not proportional to the compound coverage on the surface and that the lower workfunction material dominates the secondary electron cut-off. As a consequence the contribution of the high workfunction material to the overall workfunction distribution can be overlooked.