Pentacene thin-film transistors with solgel derived amorphous Ba0.6Sr0.4TiO3 gate dielectric
An amorphous Ba0.6Sr0.4TiO3 (BST) film with the thickness of 200nm was deposited on indium-tin-oxide (ITO)-coated glass substrate through solgel route and post-annealing at 500C. The dielectric constant of the BST film was determined to be 20.6 at 100kHz by measuring the Ag/BST/ITO parallel plate capacitor, and no dielectric tunability was observed with the bias voltage varying from ?5 to 5V. The BST film shows a dense and uniform microstructure as well as a smooth surface with the root-mean-square (RMS) roughness of about 1.4nm. The leakage current density was found to be 3.510?8A/cm2 at an applied voltage of ?5V. The transmittance of the BST/ITO/glass structure is more than 70% in the visible region. Pentacene based transistor using the as-prepared BST film as gate insulator exhibits a low threshold voltage of ?1.3V, the saturation field-effect mobility of 0.68cm2/Vs, and the current on/off ratio of 3.6105. The results indicate that the solgel derived BST film is a promising high-k gate dielectric for large-area transparent organic transistor arrays on glass substrate.
pentacene gate dielectric solgel routes (ba sr)tio3 optical transmittance organic thin film transistors