Nanoscale Quantized Oscillations in Thin‐Film Growth Greatly Enhance Transconductance in Organic Transistors

Abstract

AbstractA growth mode of pentacene thin films deposited by high vacuum sublimation where the morphology versus thickness h “rings” back and forth between rough 3D films with pyramid islands and smooth 2D films with ziqqurat islands is discovered. The roughness σ versus h exhibits seamless coherent oscillations whose amplitude and wavelength increase as integer multiples of 1.5 ML thickness. The quantized oscillations are reconducted to dynamic wetting/dewetting transitions involving the upper layers of pentacene film. Importantly, the transconductance of organic field effect transistors, either in solid state or electrolyte‐gated, exhibits antiphase oscillations with one‐decade swing. Charge mobilities in the wetting regime reach 0.1 cm2 V−1 s−1, in line with high‐end values reported for thin‐film pentacene transistors. Controlling this growth mode enables the limitations of charge transport imposed by the roughening transition to be overcome, a universal feature of high vacuum growth to date.