Operational and environmental stability of pentacene thin-film transistors

We report the effects of repeated stressing and environmental exposure on the operational stability of pentacene thin-film transistors (TFTs). Pentacene TFT channels were deposited by thermal evaporation and by spin coating and thermally converting soluble precursors. For a given dielectric thickness and applied voltage, pentacene TFTs with shorter channel lengths and therefore higher current densities have the largest decrease in field-effect mobility, on-current, and subthreshold slope and the largest threshold voltage shift with device cycling. Devices measured in ambient nitrogen show little degradation and devices fabricated on thinner dielectrics, operated at lower voltages with similarly high current densities in air, show reduced degradation. These results are consistent with degradation by thermal oxidation and suggest that reducing the operational power (by device scaling) and limiting channel exposure to ambient air improves device stability. (c) 2005 American Institute of Physics.