Moisture-induced hysteresis of pentacene thin film transistors with cross-linked poly(4-vinylphenol) gate dielectrics.

The time variable electrical characteristics of pentacene thin-film transistors (TFTs) with poly(4-vinylphenol) gate dielectrics were investigated under various relative humidity conditions and the effect of moisture on the hysteresis behavior of the pentacene TFTs was studied. One possible cause of the hysteresis behavior is the presence of inherent hydroxyl groups in bulk or surface of the polymeric dielectric, which make the gate dielectric polar, but the hysteresis behavior of the pentacene TFTs was found to depend strongly on the relative humidity and to increase with an increase of the moisture in the surrounding atmosphere. With a time-scalable investigation, it was also found that the adsorption of moisture onto the pentacene layer is the main reason for the hysteresis even with the -OH rich polymeric dielectric. The hysteresis behavior was found to be significantly reduced by suppression of moisture or other moisture-induced impurities, such as the encapsulation of the devices with glass.