The effective synthesis of two-dimensional transition metal dichalcogenides alloy is essential for successful application in electronic and optical devices based on a tunable band gap. Here we show a synthesis process for Mo1−xWxS2 alloy using sulfurization of super-cycle atomic layer deposition Mo1−xWxOy. Various spectroscopic and microscopic results indicate that the synthesized Mo1−xWxS2 alloys have complete mixing of Mo and W atoms and tunable band gap by systematically controlled composition and layer number. Based on this, we synthesize a vertically composition-controlled (VCC) Mo1−xWxS2 multilayer using five continuous super-cycles with different cycle ratios for each super-cycle. Angle-resolved X-ray photoemission spectroscopy, Raman and ultraviolet–visible spectrophotometer results reveal that a VCC Mo1−xWxS2 multilayer has different vertical composition and broadband light absorption with strong interlayer coupling within a VCC Mo1−xWxS2 multilayer. Further, we demonstrate that a VCC Mo1−xWxS2 multilayer photodetector generates three to four times greater photocurrent than MoS2- and WS2-based devices, owing to the broadband light absorption.

A process for the self-limited layer synthesis (SLS) of WSe 2 on SiO 2 substrates has been developed that provides systematic layer number controllability with micrometer-scale (>90%) and wafer-scale (∼8 cm) uniformity suitable electronic and optoelectronic device applications. This was confirmed by the fabrication and testing of a WSe 2 back-gated field effect transistor (FET) using Pd (30 nm) as the contact metal, which exhibited p-type behavior with an on/off ratio of ∼10 6 and a field-effect hole mobility of 2.2 cm 2 V −1 s −1 value, which was higher than has been reported for WSe 2 -based FETs produced by conventional chemical vapor deposition. On the basis of these results, it is proposed that the SLS method is universally applicable to a range of device applications.

The effects of Ta incorporation in La2O3 gate dielectric of amorphous InGaZnO thin-film transistor are investigated. Since the Ta incorporation is found to effectively enhance the moisture resistance of the La2O3 film and thus suppress the formation of La(OH)3, both the dielectric roughness and trap density at/near the InGaZnO/dielectric interface can be reduced, resulting in a significant improvement in the electrical characteristics of transistor. Among the samples with different Ta contents, the one with a Ta/(Ta + La) atomic ratio of 21.7% exhibits the best performance, including high saturation carrier mobility of 23.4 cm2/V·s, small subthreshold swing of 0.177 V/dec, and negligible hysteresis. Nevertheless, excessive incorporation of Ta can degrade the device characteristics due to newly generated Ta-related traps.

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Due to the advantages of being light, conformable, nonfragile, and bendable, flexible electronic devices have been considered for various applications such as flexible displays, bendable memories, e-textiles, radio frequency identifications (RFIDs), artificial skin/muscles, and wearable electronics. [1,2] Compared to rigid devices, the main challenges of flexible devices are finding suitable materials and fabrication methods to overcome the inherent barrier of low glass-transition temperature (T g ) for flexible substrates.Organic small molecules and polymers are flexible, but the corresponding devices are subject to issues resulting from short lifetime and difficult packaging. Conventional hydrogenated amorphoussilicon (a-Si:H) thin-film transistors (TFTs) can be prepared on flexible plastic substrates due to the low processing temperature of plasma-enhanced chemical vapor deposition (PECVD) (<200 C). [3] However, reduced carrier mobility and unstable characteristics under gate-bias stress limit their applications in flexible electronics. [4] Although low-temperature polysilicon (LTPS) TFTs show high mobility and stable characteristics, they are still unsuitable for flexible devices due to the crystallization temperature of polysilicon being higher than the T g of plastic substrates. [5,6] In addition, nanocrystalline-silicon (nc-Si) TFTs can show both good device stability and high carrier mobility (>10 2 cm 2 V À1 s À1 ). However, their high cost is a huge obstacle for industrial production, and the growth rate of nc-Si still requires further enhancement.Transparent oxide semiconductors (TOSs) have attracted considerable research interest because of their superior controllability in carrier generation and excellent optical transparency in the whole visible region. TFTs based on TOSs, such as InGaZnO, GaSnZnO, and AlSnZnInO, have been intensively studied due to the lower processing temperature than nc-Si TFTs, better uniformity than LTPS TFTs, and higher mobility and better stability than a-Si:H TFTs. [7][8][9] Among the state-of-the-art semiconductor materials, amorphous InGaZnO (a-IGZO), which was first fabricated by Nomura et al. in 2003, [10] is one of the most promising options, with an a-IGZO TFT successfully prepared on a flexible polyethylene terephthalate (PET)