Dynamic Variation of Rectification Observed in Supramolecular Mixed Mercaptoalkanoic Acid

Functionality in molecular electronics relies on inclusion of molecular orbital energy level within a transmission window. This can be achieved by designing the active molecule with accessible energy levels or by widening the window. While many studies have adopted the first approach, the latter is challenging because defects in the active molecular component cause low breakdown voltages. Here, it is shown that control over the packing structure of monolayer via supramolecular mixing transforms an inert molecule into a highly tunable rectifier. Binary mixed monolayer composed of alkanethiolates with and without carboxylic acid head group as a proof of concept is formed via a surface-exchange reaction. The monolayer withstands high voltages up to |4.5 V| and shows a dynamic rectification-external bias relationship in magnitude and polarity. Sub-highest occupied molecular orbital (HOMO) levels activated by the widened transmission window account for these observations. This work demonstrates that simple supramolecular mixing can imbue new electrical properties in electro-inactive organic molecules. A mixed monolayer composed of alkanethiolates with and without carboxylic acid head group is created via surface-exchange reactions. The monolayer withstands high voltages, showing dynamic rectification-voltage relationship, attributed to sub-highest occupied molecular orbital (HOMO) levels activated by the widened bias window. This work demonstrates that control over packing structure of monolayer enables the conversion of inert molecules into rectifiers.image