Effects of Substrate Morphology on the Structure of Pentacene Thin Films

Organic molecule thin films hold great promise in applications such as lightweight and flexible electronics. Previous research has demonstrated that substrate surface features such as steps affect the structural properties of such films, influencing their electrical transport characteristics and overall device efficiency. Here we present a thorough investigation into the morphology of pentacene thin films at various thicknesses on multiple substrates. Pentacene thin films were deposited on glass, quartz, and mica substrates by physical vapor deposition with nominal thicknesses of 1 - 50 nm. Their morphologies were analyzed using atomic force microscopy. We found that the root mean squared (RMS) roughness of films deposited on glass substrates initially increased as a function of nominal thickness before eventually stabilizing. We also provide a comparison between film growth on quartz, which features numerous flat terraces, and mica, known for its atomically flat surface. Pentacene films grown on quartz substrates exhibited a higher RMS roughness than those on mica substrates, suggesting a more uniform coverage on the mica as opposed to small clusters present on the quartz substrates. The study paves the way for future research into electronic characteristics.