Design and Engineering of Semiconductor-Organic Interfaces: Multilayer Synthesis on the Si(001) Surface Based on Cyclooctyne Chemistry.

ConspectusIn this Account, we will focus on how chemoselective strategies were employed for the controlled synthesis of organic multilayers on silicon, thus forming well-defined semiconductor-organic interfaces. We will start with the chemoselective [2 + 2] cycloaddition of functionalized cyclooctynes to Si-Si dimers which was used as the key step for the surface-orthogonal first layer attachment of bifunctional organic molecules to the Si(001) surface. It results in well-ordered monolayers of bifunctional molecules on the highly reactive Si(001) surface, which serve as a starting point for the further layer-by-layer growth.Various strategies for the covalent attachment of further molecular layers are then developed; they include, among others, a combination of UHV- and solution-based chemistry for the application of selective and orthogonal reaction schemes in solution as well as a carefully tuned enolether/tetrazine cycloaddition for click chemistry under UHV conditions.In particular, well-ordered multilayers of organic molecules were realized on prefunctionalized Si(001) via a two-step reaction cycle in solution. Alternating the application of two selective, orthogonal reaction steps based on asymmetric building blocks led to a well-controlled layer-by-layer growth of organic molecular layers on Si(001).Further exploitation of these strategies, e.g., in the framework of on-surface synthesis, will be discussed; our approach for the selective growth of covalently bound layers perpendicular to the surface might be further combined with lateral structuring of the surface for the synthesis of organic architectures with control in all three dimensions.