Reversibly switching the work function of tetrachloropyrazine on Pt(111)

The functionality of organic electronic devices is to a large extent governed by the properties of its organic-inorganic interfaces. These properties are mainly determined by the structure and chemical composition of the interface. To date, research has mainly focused on controlling the structure and chemistry of the adlayer to tailor the interface properties. Here, we go one step further and investigate a system with switchable interface properties.

We realize such a switchable interface with tetrachloropyrazine (TCP) on Pt(111). TCP can either chemisorb or physisorb on the Pt(111) surface, forming a double-well potential. The two minima exhibit different adsorption geometries. These allow forming diverse interface structures with notably different work function changes and coherent fractions (obtained by X-ray standing wave measurements) which can be reversibly switched.

To model this switchable interface, we apply an extended version of the SAMPLE approach which facilitates structure search for commensurate as well as higher-order commensurate adlayers. This yields three different classes of interface structures with varying work function changes and coherent fractions. We demonstrate that external stimuli, such as temperature and pressure, enable reversible switching between these different classes in order to create a dynamic interface for applications in organic electronics.