Growth Behavior of Rubrene Thin Films on Hexagonal Boron Nitride in the Early Stage

Abstract

Comprehensive SummaryTwo‐dimensional materials, with an in‐plane ordered and dangling‐bonding‐free surface, are ideal substrates for fabricating high‐ quality crystalline thin films. Here, we show a systematic study on the growth of a benchmark organic semiconductor, rubrene, on hexagonal boron nitride (h‐BN) substrate via physical vapor deposition from the initial amorphous phase to the final crystalline phase; the role of temperature in such transition and the epitaxy relationship between rubrene and h‐BN are revealed. With the increase of substrate temperature, the critical thickness of amorphous‐crystalline‐transition decreases and the morphology of crystalline phase also evolves from porous to terrace‐like. When substrate temperature reaches >100°C, the critical thickness reduces to only 0.5 nm and a precise layer‐by‐layer growth from the very first layer is achieved, which is quite rare for rubrene growing on other substrates. The high ordering can be attributed to the fine epitaxy relationship between rubrene films and the h‐BN surface lattice, and this film demonstrates good charge transport ability with a p‐type field‐effect mobility of >1 cm2·V–1·s–1.