SuMBE based organic thin film transistors

Abstract

We report on the correlation between structural and electrical properties of pentacene thin film transistors fabricated by the novel supersonic molecular beam epitaxy (SuMBE) technique. We exploited the ability of SuMBE that, through the control on the molecular precursors in the beam, allows improving the quality in terms of structure and morphology of the semi-conducting thin films compared to the more standard OMBE growth. Different growth conditions were explored to find the better range of beam parameters improving the performance of the TFT device whereas the quality of the films grown was studied by atomic force microscopy. We show that the initial kinetic energy of the pentacene molecule strongly affects both the morphology of the films and the electrical properties of the devices that result to be strongly correlated. With our FET devices prepared, on SiO 2/Si and top Au contact, we achieved the very promising field effect mobility larger than 0.5 cm 2 V −1 s −1 for films grown at room temperature at a pentacene kinetic energy of about 5.5 eV that are characterized by large crystalline grains (>2 μm).