Flexible Low-Voltage Polymer Thin-Film Transistors Using Supercritical CO2-Deposited ZrO2 Dielectrics

The fabrication of low-voltage flexible organic thin film transistors using zirconia (ZrO2) dielectric layers prepared via supercritical fluid deposition was studied. Continuous, single-phase films of approximately 30 nm thick ZrO2 were grown on polyimide (PI)/aluminum (Al) substrates at 250 degrees C via hydrolysis of tetrakis(2,2,6,6-tetramethyl-3,5-heptane-dionato) zirconium in supercritical carbon dioxide. This dielectric layer showed a high areal capacitance of 317 nF cm(-2) at 1 kHz and a low leakage current of 1.8 x 10(-6) A cm(-2) at an applied voltage of -3 V. By using poly(3-hexylthiophene) (P3HT) as a semiconductor, we have fabricated flexible thin film transistors operating at V-DS = -0.5 V and V-G in a range from 0.5 V to -4 V, with on/off ratios on the order of 1 x 10(3) and mobility values higher than 0.1 cm(2)/(V s).