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We report the simple, low-cost, and parallel fabrication of patterned organic-inorganic thin-film transistors (TFTs) by microcontact printing a molecular template on the substrate surface prior to film deposition. We printed molecules with hydrophobic tail groups on the gate oxide surfaces of TFTs to chemically, differentiate the substrate surface and confine the self-assembly of thin films, deposited from solutions flooded across the entire surface, to the transistor channels. TFTs are fabricated with good device characteristics and no current leakage. This process is more general to the patterning of other solution-deposited thin-film materials. © 2001 American Institute of Physics.

We report ambipolar transport in bottom gold contact, pentacene field-effect transistors (FETs) fabricated by spin-coating and thermally converting its precursor on a benzocyclobutene/SiO2 gate dielectric with chemically modified source and drain electrodes. A wide range of aliphatic and aromatic self-assembled thiolate monolayers were used to derivatize the electrodes and all enhanced electron and hole currents, yet did not affect the observable thin film morphology. Hole and electron mobilities of 0.1–0.5 and 0.05–0.1 cm2/V s are achieved, though the threshold for electron transport was >80 V. These ambipolar FETs are used to demonstrate inverters with gains of up to 94.

Reported here is the fabrication of 20–100nm channel length pentacene field-effect transistors (FETs) with well-behaved current-voltage characteristics. Using a solution deposition method, pentacene grains span entire devices, providing superior contacts. Varying the gate oxide thickness, the effects of scaling on transistor performance is studied. When the channel length to oxide thickness exceeds 5:1, electrostatically well-scaled nanometer FETs are prepared. The results show that the device characteristics are dominated by the contacts. Decreasing the oxide thickness lowers the device turn-on voltage beyond simple field scaling, as sharper bending of the gate potential lines around the contacts more effectively reduces the molecule/source interfacial resistance.

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.