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Pentacene organic thin-film transistors (OTFTs) with fluorinated high-κ HfLaO as gate insulator were fabricated. The dielectrics were prepared by sputtering method and then annealed in N 2 or NH 3 at 400 • C. Subsequently, the dielectrics were treated by fluorine plasma for different durations (100, 300, and 900 s). The N 2 and NH 3 -annealed OTFTs with a 100-s plasma treatment achieve a carrier mobility of 0.62 and 0.66 cm 2 /V · s, respectively, which are higher than those of the OTFTs without plasma treatment (0.22 and 0.41 cm 2 /V · s). Moreover, the plasma-treated OTFTs realize better 1/f noise characteristics than those without plasma treatment. The improved performance is due to passivation of the dielectric surface by plasma-induced fluorine incorporation. However, for longer time (300 and 900 s) of plasma treatment, the performance of the OTFTs deteriorates in terms of carrier mobility and 1/f noise characteristics due to increased plasma-induced damage of the dielectric surface. The morphology of the pentacene film grown on the HfLaO gate insulator was characterized by SEM. It reveals that the pentacene film has larger grain size and smoother surface on the HfLaO dielectric (for both annealing gases) with 100-s plasma treatment than the others (0, 300, and 900 s). Finally, AFM characterization of the HfLaO film also confirms the damaging effect of excessive plasma treatment on the dielectric.

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OTFTs with P3HT as organic semiconductor and HtTiO as gate dielectric have been studied in this work. The HtTiO dielectric film was prepared by RF sputtering of Hf and DC sputtering of Ti at room temperature. Subsequently, the dielectric film was annealed in an NUl or N 2 ambient at 200°C. Then a layer of OTS was deposited by spin-coating method to improve the surface characteristics of the gate dielectric. Afterwards, P3HT was deposited by spin-coating method. The OTFTs were characterized by I-V measurement and 1/f noise measurement. The OTFT with gate dielectric annealed in NH l displays higher carrier mobility, smaller threshold voltage, smaller sub-threshold swing, and lower 1/f noise level than the OTFT annealed in N 2 • Moreover, the HtTiO dielectric film annealed in NUl shows higher dielectric constant. In summary, HtTiO film annealed in NH l at low temperature is a promising candidate to act as the gate dielectric of high-quality low-voltage OTFTs.