Tzong-Ming Lee

High-Performance Flexible a-IGZO TFTs Adopting Stacked Electrodes and Transparent Polyimide-Based Nanocomposite Substrates

We demonstrated flexible amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) on fully transparent and high-temperature polyimide-based nanocomposite substrates. The flexible nanocomposite substrates were coated on the carrier glass substrates and were debonded after the TFT microfabrication. The adoption of the Ti/IZO stacked electrodes as source/drain/ gain electrodes significantly improved the etching compatibility with other material layers, enabling successful implementation of flexible a-IGZO TFTs onto the transparent nanocomposite substrates by conventional lithographic and etching processes. The flexible a-IGZO TFTs exhibited decent mobility and mechanical bending capability. Field-effect mobility of up to 15.9 cm2/V · s, a subthreshold swing of 0.4 V/dec, a threshold voltage of 0.8 V, and an on/off ratio of >; 108 were extracted from the TFT characteristics. The devices could be bent down to a radius of curvature of 3 mm and yet remained normally functional. Such successful demonstration of flexible oxide TFTs on transparent flexible substrates using fully lithographic and etching processes that are compatible with existing TFT fabrication technologies shall broaden their uses in flexible displays and electronics.

Effects of Mechanical Strains on the Characteristics of Top-Gate Staggered a-IGZO Thin-Film Transistors Fabricated on Polyimide-Based Nanocomposite Substrates

In this paper, we had successfully implemented flexible top-gate staggered amorphous In-Ga-Zn-O (a-IGZO) thin- film transistors (TFTs) on colorless and transparent polyimide (PI)-based nanocomposite substrates using fully lithographic and etching processes that are compatible with existing TFT mass fabrication technologies. The use of the selectively coated release layer between the nanocomposite PI film and the glass carrier ensured smooth debonding of the plastic substrate after TFT fabrication. The TFTs showed decent performances (with mobility >; 10 cm2/V · s) either as fabricated or as debonded from the carrier glass. By bending the devices to different radii of curvature (from a flat state to an outward bending radius of 5 mm), influences of mechanical strains on the characteristics of flexible a-IGZO TFTs were also investigated. In general, the mobility of the flexible a-IGZO TFT increased with the tensile strain, whereas the threshold voltage decreased with the tensile strain. The variation of the mobility in a-IGZO TFTs versus the strain appeared smaller than those observed for amorphous silicon TFTs.

Novel near-infrared and multi-colored electrochromic polybenzoxazines with electroactive triarylamine moieties

Two triarylamine-containing flexible polybenzoxazine films with Tg up to 312 °C were prepared by the thermally induced curing reaction of the corresponding polybenzoxazine precursors, which were synthesized by the reaction of paraformaldehyde with bisphenol A and 4,4′-diamino-4′′-methoxytriphenylamine (1) or N,N′-bis(4-aminophenyl)-N,N′-di(4-methoxyphenyl)-1,4-phenylenediamine (2). By introduction of triarylamine units into the polybenzoxazine precursors, the resulting solution-processable polybenzoxazine precursor films not only exhibited interesting multi-colored electrochromic behavior with a high contrast ratio both in the visible range and near infrared region (NIR) but also could effectively increase the oxidation stages when compared with their corresponding polyamides.

Novel solution-processable functional polyimide/ZrO2 hybrids with tunable digital memory behaviors

A series of solution-processable sulfur-containing poly(o-hydroxy-imide)s 3SOH-RPI with pendant hydroxyl groups and the corresponding 3SOH-RPI/ZrO2 polyimide (PI) hybrids were synthesized from the diamine 3SOH-DA and dianhydrides of CHDA, 6FDA, and DSDA, respectively, for memory application. By introducing acceptors with different electron-withdrawing capabilities (CHDA < 6FDA < DSDA) into polyimide backbones, the obtained polymer memory devices show the memory behaviors of none, DRAM, and SRAM, respectively. In order to facilitate and enhance the memory effects, different amounts of ZrO2 were incorporated into 3SOH-RPI to investigate the corresponding memory properties. The hydroxyl groups on the backbone of 3SOH-RPI could provide reaction sites for organic–inorganic bonding and the homogeneous hybrid thin films could therefore be obtained by controlling the mole ratio of zirconium butoxide/hydroxyl groups via a sol–gel reaction. The resulting PI hybrid films displayed electrically programmable digital memory properties from DRAM, SRAM, to WORM with a high ON/OFF current ratio by controlling the content of ZrO2 from 0 wt% to 30 wt%. Moreover, in order to deeply confirm the memory switching mechanism of 3SOH-RPI/ZrO2 hybrids, the devices fabricated both from PI/ZrO2 and PI/TiO2 hybrid films were used to demonstrate the effect of LUMO energy levels of ZrO2 and TiO2 on the memory characteristics and retention time in this study.

61.4: High‐Performance and Highly Rollable a‐IGZO TFTs Adopting Composite Electrodes and Transparent Polyimide Substrates

We have demonstrated high-performance and highly rollable flexible oxide TFTs on fully transparent/colorless polyimide substrates by adopting lithographic and etching processes and composite electrodes. The TFTs exhibited a field-effect mobility of up to 15.9 cm2/Vs, a sub-threshold swing of 0.43 V/decade, and an on/off ratio of > 108. The devices could be bent down to a radius of 3 mm and yet remained normally functional.