Study on fabrication and reliability of large-area CVD-grown $MoS_2$ flexible TFT array for display application

Abstract

Transition metal dichalcogenides (TMDCs) semiconductors offer substantial advantages for the next-generation electronic systems. Because of their stable semiconducting characteristics, superior mobility and current driving ability, TMDCs semiconductors are prominent candidates to replace conventional amorphous silicon (a-Si:H) for high-performance OLED display backplanes. In addition to robust electrical properties, their atomically thin nature allows physically flexible and transparent displays that are leading applications among the flexible electronics. With mature synthesis and transfer techniques, there have been several successful results of prototype semiconductor devices based on TMDCs, especially $MoS_2$. However, most of the previous studies have been implemented with micron-scale mechanically exfoliated flakes, which lack reproducibility, although electronic systems including display backplanes mostly consist of numerous transistor groups on a large substrate. In this study, synthesizing of mm-scale large-area $MoS_2$ thin film through chemical vapor deposition (CVD), fabrication of flexible $MoS_2$ thin-film transistor (TFT) and OLED driving circuit arrays on polyimide substrates and device characterization would be covered. In conclusion, intrinsic properties of the $MoS_2$ thin film were maintained during the proposed device fabrication process, which minimized device failure. Fabricated TFTs showed sufficient driving current ($~ 240 \mu A$ @ VD = 5 V) and on/off ratio (~ $10^9$) even under bending radii of 3.5 mm (induced strain of 1.82 %). Moreover, practical 2T OLED driving scheme measurement was implemented with or without strain and fabricated circuit successfully demonstrated high driving current, extremely confined off-state leakage and precise gray scale control. Based on these results, it is expected that $MoS_2$ could contribute to realization of flexible and transparent OLED based high-performance displays or electronic systems in the near future.