From a bistable adsorbate to a switchable interface: tetrachloropyrazine on Pt(111).

Lukas Hörmann,Andreas Jeindl,Oliver Hofmann

doi:10.1039/d1nr07763e

Abstract

Virtually all organic (opto)electronic devices rely on organic/inorganic interfaces with specific properties. These properties are, in turn, inextricably linked to the interface structure. Therefore, a change in structure can introduce a shift in function. If this change is reversible, it would allow constructing a switchable interface. We accomplish this with tetrachloropyrazine on Pt(111), which exhibits a double-well potential with a chemisorbed and a physisorbed minimum. These minima have significantly different adsorption geometries allowing the formation of switchable interface structures. Importantly, these structures facilitate different work function changes and coherent fractions (as would be obtained from X-ray standing wave measurements), which are ideal properties to read out the interface state. We perform surface structure search using a modified version of the SAMPLE approach and account for thermodynamic conditions using ab initio thermodynamics. This allows investigating millions of commensurate as well as higher-order commensurate interface structures. We identify three different classes of structures exhibiting different work function changes and coherent fractions. Using temperature and pressure as handles, we demonstrate the possibility of reversible switching between those different classes, creating a dynamic interface for potential applications in organic electronics.

Highlights

Organic/inorganic interfaces are essential for the construction of organicelectronic devices
When investigating the adsorption of single molecules, we are interested in the local minima of the potential energy surface (PES), which constitute energetically favourable adsorption geometries
We determine the geometries in two steps: initially, a Gaussian-process regression (GPR) algorithm identifies the minima geometries of a coarse-grained PES

Summary

Introduction

Organic/inorganic interfaces are essential for the construction of organic (opto)electronic devices. To date research has mainly focused on attaining specific interface properties through controlling the structure and chemistry of the organic adlayer.[1–5]. In this theoretical study we go beyond these efforts and study organic adsobate layers with switchable properties. Switchable interfaces in the literature rely on several function principles including modifying interactions at the interface[6] and applying external stimuli such as optical signals,[7,8] electric fields,[9,10] magnetic fields,[11] temperature,[12] biochemical processes,[13] or pH-value.[14]. We use temperature and pressure to switch adlayers of molecules that exhibit a doublewell potential when adsorbing on a substrate. Examples for systems with double-well potentials include benzene derivatives on Pt(111),[15–17] tetrafluoropyrazine on Ni(111)[18] and anthradithiophene on Cu(111).[19–21]. Related examples are molecules adopting different conformers upon adsorption.[22] Examples for systems with double-well potentials include benzene derivatives on Pt(111),[15–17] tetrafluoropyrazine on Ni(111)[18] and anthradithiophene on Cu(111).[19–21] Related examples are molecules adopting different conformers upon adsorption.[22]

Methods

Results

Conclusion