Crystallization of rubrene on a nanopillar-templated surface by the melt-recrystallization process and its application in field-effect transistors†
We present an approach to fabricate a continuous and crystalline rubrene film using the melt-recrystallization process with the assistance of a silicon nanopillar template. Better film morphology, enhanced crystallinity, and mainly oriented crystallites with the c-axis of the orthorhombic rubrene aligning parallel to the nanopillars were obtained as compared to that on a planar substrate. The oriented crystal growth is further modulated by the surface modification. It is suggested that the sidewalls of nanopillars play a key role in mediating the switch of crystal orientation and crystal growth. The obtained nanopillar-templated rubrene film was used to fabricate a vertical field-effect transistor. The device gave a current density of 78 mA cm−2, on–off ratio around 103−4, subthreshold swing of 89.1 mV per decade and transconductance of 154.9 mS cm−2 on an ODTS-modified substrate surface.