High-performance Indium Gallium Zinc Oxide Research Articles

Optimization of Dual-Fuel Combustion Synthesis for Rapid Formation of Solution-Processed Metal-Oxide Thin-Film Transistors

Solution processing of metal-oxide semiconductors has received significant attention in various fields of electronics owing to its advantages such as simple fabrication process, large-area scalability, and facile stoichiometric tunability. However, the conventional sol–gel route requires a relatively long annealing time to obtain a low-defect film with high density and sufficient amount of metal–oxygen–metal bonding state, which prevents implementation in cost-effective continuous manufacturing. Here, we report rapid formation of solution-processed oxide semiconductors by employing a dual-fuel-based solution combustion synthesis route. In particular, by optimizing the ratio of dual fuels of acetylacetone and 1,1,1-trifluoro-acetylacetone (molar ratio of 7:3), high-performance indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs) could be fabricated at 350 °C with the annealing time as short as 5 min (In:Ga:Zn = 0.68:0.1:0.22). Based on spectroscopic analysis, it was found that the dual fuels enabled rapid formation of the metal–oxygen–metal lattice structure with low defective oxygen bonding states. The IGZO TFTs fabricated with an optimized fuel ratio exhibited average field-effect mobilities of 1.11 and 3.69 cm2 V–1 s–1 with annealing times of 5 and 20 min, respectively (averaged in 9∼12 devices). Also, in the case of the 5 min annealed device, the threshold voltage was −0.48 ± 1.96 V, showing enhancement-mode operation. Furthermore, the device showed good stability against both positive gate bias stress and negative gate bias stress conditions with small threshold voltage shifts of −1.28 and – 1.28 V in 5760 s, respectively.

High-Performance IGZO Nanowire-Based Field-Effect Transistors with Random-Network Channels by Electrospun PVP Nanofiber Template Transfer.

A random network of indium–gallium–zinc oxide (IGZO) nanowires was fabricated by electrospun-polyvinylpyrrolidone (PVP)-nanofiber template transfer. Conventional electrospun nanofibers have been extensively studied owing to their flexibility and inherently high surface-to-volume ratio. However, solution-based IGZO nanofibers have critical issues such as poor electrical properties, reliability, and uniformity. Furthermore, high-temperature calcination, which is essential for vaporizing the polymer matrix, hinders their applications for flexible electronics. Therefore, sputter-based IGZO nanowires were obtained in this study using electrospun PVP nanofibers as an etching mask to overcome the limitations of conventional electrospun IGZO nanofibers. Field-effect transistors (FETs) were fabricated using two types of channels, that is, the nanofiber template-transferred IGZO nanowires and electrospun IGZO nanofibers. A comparison of the transmittance, adhesion, electrical properties, reliability, and uniformity of these two channels in operation revealed that the nanofiber template-transferred IGZO nanowire FETs demonstrated higher transmittance, stronger substrate adhesion, superior electrical performance, and operational reliability and uniformity compared to the electrospun IGZO nanofiber FETs. The proposed IGZO nanowires fabricated by PVP nanofiber template transfer are expected to be a promising channel structure that overcomes the limitations of conventional electrospun IGZO nanofibers.

High-Performance Inkjet-Printed Indium-Gallium-Zinc-Oxide Transistors Enabled by Embedded, Chemically Stable Graphene Electrodes.

Recent developments in solution-processed amorphous oxide semiconductors have established indium-gallium-zinc-oxide (IGZO) as a promising candidate for printed electronics. A key challenge for this vision is the integration of IGZO thin-film transistor (TFT) channels with compatible source/drain electrodes using low-temperature, solution-phase patterning methods. Here we demonstrate the suitability of inkjet-printed graphene electrodes for this purpose. In contrast to common inkjet-printed silver-based conductive inks, graphene provides a chemically stable electrode-channel interface. Furthermore, by embedding the graphene electrode between two consecutive IGZO printing passes, high-performance IGZO TFTs are achieved with an electron mobility of ∼6 cm(2)/V·s and current on/off ratio of ∼10(5). The resulting printed devices exhibit robust stability to aging in ambient as well as excellent resilience to thermal stress, thereby offering a promising platform for future printed electronics applications.

Passivation and Annealing for Improved Stability of High Performance IGZO TFTs

ABSTRACTThe influence of annealing ambient conditions and deposited passivation materials on indium-gallium-zinc-oxide (IGZO) thin-film transistor (TFT) performance is investigated. Results from annealing experiments confirm that a nominal exposure to oxidizing ambient conditions is required, which is a function of temperature, time and gas environment. Nitrogen anneal with a controlled air ramp-down provided the best performance devices with a mobility (µsat) of 11-13 cm2/V·s and subthreshold slope (SS) of 135-200 mV/dec, with some hysteresis. Plasma-deposited passivation materials including sputtered quartz and PECVD SiO2 demonstrated a significant increase in material conductivity, which was not significantly reversible by an oxidizing ambient anneal. E-beam evaporated Al2O3 passivated devices that were annealed in air at 400 °C demonstrated improved stability over time and suppressed hysteresis in comparison to unpassivated devices. Devices which were passivated with B-staged bisbenzocyclobutene-based (BCB) resins and annealed in air at 250 °C also exhibited suppressed hysteresis.