Low-voltage organic devices based on pristine and self-assembled monolayer-treated HfTiO_x gate dielectrics

Low-voltage organic field-effect transistors (OFETs) and complementary metal oxide semiconductor (CMOS) inverters based on pentacene and N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13) were fabricated on HfTiO_x gate dielectrics. Both pristine dielectrics and substrates passivated with self-assembled monolayers (SAMs) of n-dodecylphosphonic acid (PA-C12) were employed. The high capacitance and low leakage current of the HfTiO_x-based dielectrics enabled the devices to operate at |V| < 3 V. Passivation with PA-C12 was highly effective in improving the device characteristics. In particular, an electron mobility of 0.72 cm² V^-1 s^-1 was measured for the device fabricated with the passivated HfTiO_x dielectric, which represents the best performance reported to date for perylene-based OFETs prepared with thin, high-k gate dielectrics. The CMOS inverters exhibited fast switching and high gain characteristics, which were attributed to good coupling between the optimized p- and n-type OFETs.