Abstract: The last decade has seen explosive growth in both the materials and the processing of organic semiconductors. Relatively ignored is the surface of the organic semiconductor, though the surface properties are central to function in devices. We have recently developed the ability to chemically functionalize the surface of organic semiconductors to form a monolayer not dissimilar to those found on other classic substrates. Specifically, we can tailor the surface of the acene class of organic semiconductors (tetracene, pentacene, rubrene) by using the Diels-Alder reaction, where the adsorbate is dosed in via the vapor phase and bonds at the surface. Though successful, the naivety of the approach stands in contrast to the rich complexity of the organic system and the substantial deviations organic surfaces displayed, in contrast to their inorganic brethren.

This talk summarizes many of the expected and unexpected deviations that occur because of the very different nature of the organic crystal; namely, its high anisotropy, recessed reaction loci, and weakly bound molecular units. From these experiments, we begin to assemble a mechanistic understanding of how reactions at organic surfaces occur. This chemistry is then applied to improve the metal-on-semiconductor contact. As a demonstration of principle, Diels-Alder chemistry is used to form covalent bonds linking the organic semiconductor with a deposited metal contact, thereby eliminating the poor adhesion present in this system. Application of the chemistry toward contact potential shifts concludes the talk.