Engineering gate dielectric surface properties for enhanced polymer field-effect transistor performance

The modification of silicon dioxide (SiO₂) gate dielectrics with silane self-assembled monolayers (SAMs) via silylation was conducted to study their impacts on polymer field-effect transistor (FET) performance. SAMs formed from silylating agents with long alkyl chains such as octadecyl gave high field-effect mobility but a lower on/off ratio because of lower SAM coverage of the gate dielectric surface. In contrast, SAMs from silylating agents with phenyl or medium alkyl chains (octyl) provided a high on/off ratio from high SAM surface coverage but lower mobility due to their inefficiency in promoting molecular ordering of the channel semiconductor. By treating the SiO₂ dielectric surface with two silylating agents, one with an octadecyl chain and one with an octyl or phenyl chain, in a proper sequence, a high-performance "hybrid" dual-silane SAM could be created, enabling attainment of both a high mobility and on/off ratio, together with other desirable FET properties.