Interfacial Organic Layers for Chemical Stability and Crystalline Ordering of Thiophene and Carboxyl Films on a Metal Surface

Organic-based devices require multicomponent, multilayer architectures consisting of functional molecules that may be chemically unstable at a metal interface. In this work, we demonstrate that an interfacial organic layer (IOL) provides chemical stability at and above room temperature, while also achieving desired crystalline ordering of the functionalized organic layer. As the IOL decouples organic species from direct interactions with the metal, new structural motifs become available that are not otherwise observed, yielding the first submolecular resolution imaging of phenyl-thiophene stacking at a surface. We studied self-organized layers comprising two classes of functional groups, carboxylic acids and thiophenes, which have applications in organic electronics but are each chemically unstable and structurally disordered when deposited directly onto the Cu(001) and other metal surfaces. The IOL strategy demonstrated here resolves these issues and broadens opportunities for organic thin films on metal surfaces in organic photovoltaic, organic semiconductor, catalyst, and other technologies.