Monolayer-Induced Changes in Metal Penetration and Wetting for Metal-on-Organic Interfaces

Metal deposition onto organic materials results in a myriad of issues at the metal-on-organic interface, necessitating a highly adaptable interlayer. A single cysteamine-based monolayer on evaporated tetracene thin films is demonstrated to be highly multifunctional, inhibiting metal penetration and increasing contact wetting for the silver-on-organic interface. Cross sections of the monolayer-coated sample, imaged via transmission electron microscopy, show that silver penetration decreased by up to 40% compared to untreated tetracene. Substantial morphology differences are observed between treated and untreated samples; metal poorly wets untreated samples, forming nanoparticle clusters, while monolayer-coated samples are uniform. Scanning electron microscopy indicates that the monolayers prevent contact discontinuities (hundreds of nanometers in size) that were observed on untreated samples with thin (20 nm) silver contacts. Monolayers do not add any significant barrier to charge transport compared to untreated samples, with conductivity values measured to be near identical. When these are combined with earlier reports of cysteamine improving contact adhesion and durability, monolayers can effectively address most of the issues plaguing metal-on-organic devices.