Effect of heat treatment in aluminium oxide preparation by UV/ozone oxidation for organic thin-film transistors.

Effect of heat treatment in aluminium oxide (AlOx) preparation employing UV/ozone exposure of thermally-evaporated aluminium is reported. AlOx is combined with 1-octylphosphonic acid to form a gate dielectric in low-voltage organic thin-film transistors based on pentacene. For short UV/ozone exposure times the 100 degrees C-heating step that immediately follows UV/ozone oxidation of aluminium leads to a decrease in the transistor threshold voltage of up to 8% and similar to fourfold reduction in the gate dielectric current density. Transistors with AlOx prepared by 60-minute UV/ozone oxidation do not exhibit such behaviour. These results are explained in terms of reduced density of charged oxygen vacancies in the UV/ozone oxidized AlOx.