Controlling interface polymorphism of TCNE/Cu(111) with external electric fields

Inorganic/organic interfaces can exhibit a rich variety of polymorphs, sometimes with drastic consequences for the interface properties. An example of these interfaces is tetracyanoethylene (TCNE) on Cu(111), which has recently been shown to exhibit a coverage driven phase transition from polymorphs of flat lying to standing molecules. The transition results in a change in work function of more than 3 eV, which makes this example system particularly interesting for applications in organic electronics.

In this contribution we explore how desirable polymorphs we can be stabilized using external electric fields. We employ a structure search algorithm based on a combination of density functional theory calculations and machine learning to tackle the following questions: Can we promote the formation of specific phases with electric fields? Can we create previously unseen phases with electric fields?