Myung Ho Chung

A Flexible Amorphous Bi5Nb3O15 Film for the Gate Insulator of the Low-Voltage Operating Pentacene Thin-Film Transistor Fabricated at Room Temperature

The amorphous Bi(5)Nb(3)O(15) film grown at room temperature under an oxygen-plasma sputtering ambient (BNRT-O(2) film) has a hydrophobic surface with a surface energy of 35.6 mJ m(-2), which is close to that of the orthorhombic pentacene (38 mJ m(-2)), resulting in the formation of a good pentacene layer without the introduction of an additional polymer layer. This film was very flexible, maintaining a high capacitance of 145 nF cm(-2) during and after 10(5) bending cycles with a small curvature radius of 7.5 mm. This film was optically transparent. Furthermore, the flexible, pentacene-based, organic thin-film transistors (OTFTs) fabricated on the poly(ether sulfone) substrate at room temperature using a BNRT-O(2) film as a gate insulator exhibited a promising device performance with a high field effect mobility of 0.5 cm(2) V(-1) s(-1), an on/off current modulation of 10(5), and a small subthreshold slope of 0.2 V decade(-1) under a low operating voltage of -5 V. This device also maintained a high carrier mobility of 0.45 cm(2) V(-1 )s(-1) during the bending with a small curvature radius of 9 mm. Therefore, the BNRT-O(2) film is considered a promising material for the gate insulator of the flexible, pentacene-based OTFT.

Hysteresis Effects by Source/Drain Interdigitated-Finger Geometry in 6,13-Bis(triisopropylsilylethynyl)pentacene Thin-Film Transistors

This work reports on the fabrication of organic thin-film transistors (OTFTs) with a solution-based 6,13-bis(triisopropylsilylethynyl)pentacene by a drop-casting method, and the determination of the electrical properties of OTFTs having different source/drain interdigitated-finger electrodes. The results show that the hysteresis in transfer characteristics of the OTFTs depends on the variation of contact fingers. These hystereses lead to changes in threshold voltage, which originates from charge trapping/detrapping at or near the organic semiconductor/dielectric interface. These related phenomena also influence the device parameters such as the field-effect mobility, the on/off current ratio, and the gate current.