High-resolution electrohydrodynamic inkjet printing of stretchable metal oxide semiconductor transistors with high performance

Abstract

As demands for high pixel densities and wearable forms of displays increase, high-resolution printing technologies to achieve high performance transistors beyond current amorphous silicon levels and to allow low-temperature solution processability for plastic substrates have been explored as key processes in emerging flexible electronics. This study describes electrohydrodynamic inkjet (e-jet) technology for direct printing of oxide semiconductor thin film transistors (TFTs) with high resolution (minimum line width: 2 μm) and superb performance, including high mobility (∼230 cm V s). Logic operations of the amplifier circuits composed of these e-jet-printed metal oxide semiconductor (MOS) TFTs demonstrate their high performance. Printed InO TFTs with e-jet printing-assisted high-resolution S/D electrodes were prepared, and the direct printing of passivation layers on these channels enhanced their gate-bias stabilities significantly. Moreover, low process temperatures (<250 °C) enable the use of thin plastic substrates; highly flexible and stretchable TFT arrays have been demonstrated, suggesting promise for next-generation printed electronics.

Solution‐Based Micro‐ and Nanoscale Metal Oxide Structures Formed by Direct Patterning for Electro‐Optical Applications

“…By applying a DC voltage bias between the metal nozzle and the substrate, the ink can be ejected onto the substrate. Kim et al demonstrated fine In 2 O 3 patterns by using e‐jet printing with indium nitrate hydrate as the precursor. The authors showed that the film thickness can be increased by increasing the number of printing passes; the smallest line width achievable by e‐jet printing is as small as 2 µm, as shown in Figure b.…”

“…In addition, chemical etching and photoresist (PR) stripping increase both the surface roughness and the defects in MO films. Recently, various solution direct‐patterning (SDP) techniques have been developed, such as micromolding, inkjet printing, e‐jet printing, photopatterning, and e‐beam writing . Unlike conventional photolithography, which is a subtractive process, SDP techniques are additive methods that control the liquid MO precursor to form patterns with the desired size and shape by printing, molding, selective solidification, or selective deposition.…”

Printing Silver Conductive Inks with High Resolution and High Aspect Ratio

“…High throughput gravure, and reverse‐offset printing methods have achieved a linewidth of 5 µm . Electrohydrodynamic jet printing methods have also attracted a lot of attention due to their ability to print ultranarrow lines, down to 1 µm . While this progress allows significant performance enhancement in many printable electronic devices (like thin‐film transistors), these printing processes rely on using a small amount of a low solid content ink.…”

Printable Zn2GeO4 Microwires Based Flexible Photodetectors with Tunable Photoresponses

“…Carbon nanotube, graphene, ultrathin metal nanowires, and 1D inorganic semiconductor nano/microstructures are commonly used for printable electronics. Especially, acting as the functional components, 1D inorganic semiconductors have great superiorities to construct flexible and wearable electronic devices, such as photodetectors, transistors, pressure sensors, and gas/chemical sensors . However, a second operation such as transfer from the growth substrate is always needed to assemble the flexible devices, thus possibly damages the nano/microwires and results in a performance degradation.…”