Ultra-definition, large-area displays with three-dimensional visual effects represent megatrend in the current/future display industry. On the hardware level, such a “dream” display requires faster pixel switching and higher driving current, which in turn necessitate thin-film transistors (TFTs) with high mobility. Amorphous oxide semiconductors (AOS) such as In-Ga-Zn-O are poised to enable such TFTs, but the trade-off between device performance and stability under illumination critically limits their usability, which is related to the hampered electron-hole recombination caused by the oxygen vacancies. Here we have improved the illumination stability by substituting oxygen with nitrogen in ZnO, which may deactivate oxygen vacancies by raising valence bands above the defect levels. Indeed, the stability under illumination and electrical bias is superior to that of previous AOS-based TFTs. By achieving both mobility and stability, it is highly expected that the present ZnON TFTs will be extensively deployed in next-generation flat-panel displays.

Interest in oxide semiconductors stems from benefits, primarily their ease of process, relatively high mobility (0.3–10 cm2/vs), and wide-bandgap. However, for practical future electronic devices, the channel mobility should be further increased over 50 cm2/vs and wide-bandgap is not suitable for photo/image sensor applications. The incorporation of nitrogen into ZnO semiconductor can be tailored to increase channel mobility, enhance the optical absorption for whole visible light and form uniform micro-structure, satisfying the desirable attributes essential for high performance transistor and visible light photo-sensors on large area platform. Here, we present electronic, optical and microstructural properties of ZnON, a composite of Zn3N2 and ZnO. Well-optimized ZnON material presents high mobility exceeding 100 cm2V−1s−1, the band-gap of 1.3 eV and nanocrystalline structure with multiphase. We found that mobility, microstructure, electronic structure, band-gap and trap properties of ZnON are varied with nitrogen concentration in ZnO. Accordingly, the performance of ZnON-based device can be adjustable to meet the requisite of both switch device and image-sensor potentials. These results demonstrate how device and material attributes of ZnON can be optimized for new device strategies in display technology and we expect the ZnON will be applicable to a wide range of imaging/display devices.

For practical device applications, monolayer transition metal dichalcogenide (TMD) films must meet key industry needs for batch processing, including the high‐throughput, large‐scale production of high‐quality, spatially uniform materials, and reliable integration into devices. Here, high‐throughput growth, completed in 12 min, of 6‐inch wafer‐scale monolayer MoS2 and WS2 is reported, which is directly compatible with scalable batch processing and device integration. Specifically, a pulsed metal–organic chemical vapor deposition process is developed, where periodic interruption of the precursor supply drives vertical Ostwald ripening, which prevents secondary nucleation despite high precursor concentrations. The as‐grown TMD films show excellent spatial homogeneity and well‐stitched grain boundaries, enabling facile transfer to various target substrates without degradation. Using these films, batch fabrication of high‐performance field‐effect transistor (FET) arrays in wafer‐scale is demonstrated, and the FETs show remarkable uniformity. The high‐throughput production and wafer‐scale automatable transfer will facilitate the integration of TMDs into Si‐complementary metal‐oxide‐semiconductor platforms.

We have demonstrated a self-aligned top-gate amorphous gallium indium zinc oxide thin film transistor (a-GIZO TFT). It had a field effect mobility of 5 cm2/V s, a threshold voltage of 0.2 V, and a subthreshold swing of 0.2 V/decade. Ar plasma was treated on the source/drain region of the a-GIZO active layer to reduce the series resistance. After Ar plasma treatment, the surface of the source/drain region was divided into In-rich and In-deficient regions. The a-GIZO TFT also had a constant sheet resistance of 1 kΩ/◻ for a film thickness of over 40 nm. The interface between the source/drain Mo metal and the Ar plasma-treated a-GIZO indicated a good Ohmic contact and a contact resistivity of 50 μΩ cm2.

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The effects of Ar ion and Ar gas cluster ion beam (GCIB) sputtering processes on the core-level structure, valence band structure and work function of poly (3,4-ethylenedioxythiophene) polymerized with poly (4-styrenesulfonate) (PEDOT:PSS) and multi wall carbon nanotube (MWNT)/PEDOT:PSS films were characterized by photoemission spectroscopy and atomic forced microscopy. The depth profiles of X-ray photoemission and ultraviolet spectroscopy with Ar ion sputtering process confirmed that Ar ion sputtering process highly causes damage on the surface potential and valence band structure as well as core-level structure of PEDOT:PSS film. However, on the contrary to Ar ion sputtering, Ar GCIB sputtering process at each acceleration voltage did not induce any transition of chemical bonding state in PEDOT:PSS film and therefore, the atomic composition of Ar GCIB sputtered PEDOT:PSS film was also nearly same with that of as-dep. PEDOT:PSS film. Furthermore, the valence band structure and work function of organic composite films were not damaged by Ar GCIB sputtering process so that the energy band diagram between PEDOT:PSS and fluorine doped tin oxide films was clearly settled using valence band structure and work function of Ar GCIB sputtered PEDOT:PSS film.

The band gap and defect states of MgO thin films were investigated by using reflection electron energy loss spectroscopy (REELS) and high-energy resolution REELS (HR-REELS). HR-REELS with a primary electron energy of 0.3 keV revealed that the surface F center (FS) energy was located at approximately 4.2 eV above the valence band maximum (VBM) and the surface band gap width (E g S ) was approximately 6.3 eV. The bulk F center (F B ) energy was located approximately 4.9 eV above the VBM and the bulk band gap width was about 7.8 eV, when measured by REELS with 3 keV primary electrons. From a first-principles calculation, we confirmed that the 4.2 eV and 4.9 eV peaks were F S and F B , induced by oxygen vacancies. We also experimentally demonstrated that the HR-REELS peak height increases with increasing number of oxygen vacancies. Finally, we calculated the secondary electron emission yields (γ) for various noble gases. He and Ne were not influenced by the defect states owing to their higher ionization energies, but Ar, Kr, and Xe exhibited a stronger dependence on the defect states owing to their small ionization energies. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

Introduction:In spite of the successful achievement of oxide-semiconductor (OS) technology in recent years, stability degradation especially at high mobility regime limits the application of oxide semiconductors in next generation displays. According to previous works, the instability is closely related to oxygen vacancies (V o ) causing persistent photoconductivity (PPC) [1,2]. From this point of view, zinc oxynitride (ZnON)[3] with small bandgap (1.3 eV) and high intrinsic mobility is attractive to overcome the performance issues of OS. In this paper, we report on ZnON-thin film transistors (TFTs) with field effect mobility near 100 cm 2 /Vs and operation stability(< 3 V) under light-illumination biasstress. Our results demonstrate that ZnON-TFTs are strong candidates for pixel switching devices in ultra-high definition and large area displays. ZnON film deposition and electrical properties: ZnON films were deposited by reactive rf magnetron sputtering using Zn target and Ar/O 2 /N 2 mixture gas. By varying the O 2 flow rate and deposition pressure at a fixed N 2 and Ar flow rate, the anion ratio (O/N) in ZnON was modulated, while maintaining Zn concentration at ~55 at%. As-deposited and annealed films are composed of amorphous ZnON and nanocrystallites of ZnO and Zn 3 N 2 (Fig. 1). Density functional theory (DFT)-based calculations (Fig. 2) revealed that ZnON has a smaller effective mass (0.19 m e ) than conventional OSs (0.27 m e for ZnO, 0.32~0.34 m e for GIZO[4], and 0.22 m e for In 2 O 3 ), indicating high mobility characteristics of ZnON. Hall measurements confirmed its high mobility values of 35~118 cm 2 /Vs with carrier concentrations of 7.7x10 16~3 .1x10 18 /cm 3 [Fig 3(b) and (c)]. As shown in Fig. 3, N incorporation is directly related with the enhancement of mobility and carrier concentration. ZnON-TFT fabrication and basic characteristics:We have fabricated etch-stopper (ES) type ZnON-TFTs (N/O=37/6) on 150 mm x 150 mm glass substrates by photolithography and etching processes. After patterning a sputter-deposited Mo layer for gate electrodes, plasma-enhanced chemical vapor deposition (PECVD) was used to deposit gate dielectrics of SiN x /SiO x (350 nm/50 nm). ZnON (50 nm) was subsequently sputter-deposited as the active layer. Then, 100 nm-thick PECVD SiO x was deposited and patterned to form the ES and contact regions. Mo or AlNd source/drain (S/D) electrodes were formed by sputtering and dry etching process. TFT structures are illustrated in Fig. 4. After annealing in air at 250 o C for 1 hr, we have measured I-V characteristics, including operation stabilities, in vacuum (<10 -6 Torr). Fabricated ZnON-TFTs operated in depletion mode. Thus, TFT current includes fringe component. TFTs still have mobility as high as ~100 cm 2 /Vs even after fringe current correction by channel width (W) dependent I ds -V gs analysis (Fig. 5). Transfer (I ds -V gs ) and output characteristics are given in Fig. 6(a) and (b),