Crystalline or amorphous metal oxides are widely used in various optoelectronic devices as key components, such as transparent conductive electrodes, dielectrics or semiconducting active layers for thin-film transistor (TFT) backplanes in large-area displays, photovoltaics, and light-emitting diodes. Although crystalline inorganic materials demonstrate outstanding optoelectronic performance, owing to their wide bandgaps, large conductivities, and high carrier mobilities, their inherent brittleness makes them vulnerable to mechanical stress, thereby limiting the use of metal-oxide films in emerging flexible electronic applications. In this study, stress-diffusive organicinorganic hybrid superlattice nanostructures are developed to overcome the mechanical limitation of crystalline oxides and to provide high mechanical stability to metal-oxide semiconductors. In particular, hybrid transparent superlattice electrodes based on crystalline indium-tin oxide exhibit high electrical conductivities of up to 555 S cm -1 (resistance variation < 3%) and effectively reduce the mechanical stress on the inorganic layer (up to 10 000 bending cycles with a radius of 1 mm). Furthermore, to ensure the viability of the hybrid superlattice flexible electronics, all solution-processed superlattice crystalline indium-gallium-oxide TFTs are implemented on a thin (≈5 µm) polyimide substrate, providing highly robust and excellent electrical performance (average mobility of 7.6 cm 2 V -1 s -1 ).
Solution-processed metal-oxide thin-film transistors (TFTs) with different metal compositions are investigated for ex situ and in situ radiation hardness experiments against ionizing radiation exposure. The synergetic combination of structural plasticity of Zn, defect tolerance of Sn, and high electron mobility of In identifies amorphous zinc−indium−tin oxide (Zn−In−Sn−O or ZITO) as an optimal radiation-resistant channel layer of TFTs. The ZITO with an elemental blending ratio of 4:1:1 for Zn/In/Sn exhibits superior ex situ radiation resistance compared to In−Ga− Zn−O, Ga−Sn−O, Ga−In−Sn−O, and Ga−Sn−Zn−O. Based on the in situ irradiation results, where a negative threshold voltage shifts and a mobility increase as well as both off current and leakage current increase are observed, three factors are proposed for the degradation mechanisms: (i) increase of channel conductivity, (ii) interface-trapped and dielectric-trapped charge buildup, and (iii) trap-assisted tunneling in the dielectric. Finally, in situ radiation-hard oxide-based TFTs are demonstrated by employing a radiationresistant ZITO channel, a thin dielectric (50 nm SiO 2 ), and a passivation layer (PCBM for ambient exposure), which exhibit excellent stability with an electron mobility of ∼10 cm 2 /V s and aΔV th of <3 V under real-time (15 kGy/h) gamma-ray irradiation in an ambient atmosphere.
Transparent oxide semiconductors are successfully implemented as thin‐film transistors (TFTs) for large‐area display applications with superior electrical performance in comparison with that of conventional amorphous silicon. However, further development of high‐performance oxide semiconductors is hindered by the trade‐off between mobility and stability. Mixed metal composition containing heavy metal cations shows high‐mobility/low‐stability and light metal cations exhibits low‐mobility/high‐stability. A novel material design strategy for realizing a high‐performance oxide semiconductor for TFTs through partial substitution of Se or S for O in In2O3 is reported. In contrast to the conventional small‐sized Ga substitution for suppressing oxygen vacancies, the replacement of O by Se or S results in lattice stabilization and oxygen‐vacancy suppression, consequently stabilizing Se‐ or S‐incorporated In2O3 TFTs. In2O3:Se TFTs exhibit an average field‐effect mobility of 6.1 cm2 V−1s−1, ON/OFF current ratio (Ion/Ioff) of 108, and excellent operational stability with threshold voltage shift values of <0.10 V at a positive and negative bias stress for 10 000 s. Furthermore, the seven‐stage ring oscillator circuit operating at a supply bias of 20 V exhibits an oscillation frequency of >805 kHz and a corresponding propagation delay of <90 ns per stage.
Electrical properties of metal oxide thin-film transistors (TFTs) are tuned via the microstructural control of organic back-channel passivation layers. In this study, organic semiconductor (OSC) passivation layers with various molecular...
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