Aluminium oxide prepared by UV/ozone exposure for low-voltage organic thin-film transistors

We have developed a gate dielectric for low-voltage organic thin-film transistors based on an inorganic/organic bi-layer with a total thickness of up to ~ 20 nm. The inorganic layer is aluminium oxide formed by UV/ozone treatment of aluminium layers. The organic layer is 1-octylphosphonic acid. The preparation of aluminium oxide was studied with respect to the threshold voltage of p-channel thin-film transistors based on thermally evaporated pentacene. The results demonstrate that the threshold voltage decreases with increasing UV/ozone exposure time. The threshold voltage varies by 0.7 V and the gate-source leakage current by a factor of 10 as a function of aluminium oxide preparation. The electrical breakdown field of the bi-layer gate dielectric is at least 5 MV/cm for all AlOx preparation conditions.