In this work, bottom gate top contact structured organic field-effect transistors (OFETs) were fabricated using Rubrene as active material and SiO₂ as the dielectric on n-type silicon wafer by thermal evaporation method. The effect of dielectric surface modification and abrupt heat treatment on the crystallinity of Rubrene thin film and its influence on the performance of OFETs were investigated. The surface morphologies and the crystal structure of Rubrene films were characterized using differential scanning calorimetry, X-ray diffraction (XRD) and atomic force microscopy. It is observed that the dielectric surface affects the crystalline structure of Rubrene thin film as well as the electrical performance of the OFETs. Thermal transition of Rubrene from amorphous state to highly crystalline state was observed after abrupt heat treatment. It is observed that highly crystalline Rubrene thin films can be obtained by carefully deploying the rapid heat treatment method followed by surface treatment. The electrical properties of the OFETs such as field effect mobility, threshold voltage and current on/off ratio are evaluated using the V-I characteristics and the results are compared with the published data. Improvements in the performance of OFET are evident due to the improved crystallization and highly ordered structure of Rubrene molecules.
