Effect of water in ambient air on hysteresis in pentacene field-effect transistors containing gate dielectrics coated with polymers with different functional groups

We investigated the effect of water in ambient air on the hysteresis phenomena of pentacene field-effect transistors with polymer/SiO₂ gate dielectrics. The polarity of the polymer surface was controlled by using three different polymers: poly(styrene), poly(4-hydroxy styrene), and poly(4-vinyl pyridine). Water diffusion into the interface between the pentacene and the gate dielectric was driven by the polarity of the polymer surface, resulting in considerable hysteresis and degradation of device performances. The observed hysteresis behaviors can be explained in terms of donor- and acceptor-like trap formation by water molecules that have diffused between the pentacene and the gate dielectric. The different effects of these traps on hysteresis depending on the functional groups at the polymer surface were also investigated.