Abstract:In order to progress from the lab to commercial applications it will be necessary to develop industrially scalable methods to produce large quantities of defect-free graphene.Here we show that high-shear mixing of graphite in suitable, stabilizing liquids results in large-scale exfoliation to give dispersions of graphene nanosheets. XPS and Raman spectroscopy show the exfoliated flakes to be unoxidised and free of basal plane defects. We have developed a simple model which shows exfoliation to occur once the local shear rate exceeds 10 4 s -1 . By fully characterizing the scaling behaviour of the graphene production rate, we show that exfoliation can be achieved in liquid volumes from 100s of ml up to 100s of litres and beyond. The graphene produced by this method performs well in applications from composites to conductive coatings. This method can be applied to exfoliate BN, MoS2 and a range of other layered crystals. Main Text:Due to its ultra-thin, 2-dimensional nature and its unprecedented combination of physical properties, graphene has become the most studied of all nano-materials. In the next decade graphene is likely to find commercial applications in many areas from high-frequency electronics to smart coatings.

Solution-processed semiconducting transition metal dichalcogenides (TMDs) are at the centre of an ever-increasing research effort in printed (opto)electronics. However, device performance is limited by structural defects resulting from the exfoliation process and poor inter-flake electronic connectivity.Here, we report a new molecular strategy to boost the electrical performance of TMD-based devices via the use of dithiolated conjugated molecules, to simultaneously heal sulfur vacancies in solutionprocessed transition metal disulfides (MS2) and covalently bridge adjacent flakes, thereby promoting percolation pathways for the charge transport. We achieve a reproducible increase by one order-ofmagnitude in field-effect mobility (µFE), current ratios (ION / IOFF), and switching times (τS) of liquid-gated transistors, reaching 10 -2 cm 2 V -1 s -1 , 10 4 , and 18 ms, respectively. Our functionalization strategy is an universal route to simultaneously enhance the electronic connectivity in MS2 networks and tailor on demand their physicochemical properties according to the envisioned applications.

Two-dimensional layered semiconductors have recently emerged as attractive building blocks for next-generation low-power non-volatile memories. However, Hongzhou Zhang: hozhang@tcd.ie 1 arXiv:1811.09545v1 [cond-mat.mtrl-sci] 23 Nov 2018 † J.J. and D.K. contributed equally to this project. D.K. performed electrical measurements on samples of different layer thickness and irradiation dose, as well as atomic force microscopy and scanning electron microscopy. CVD growth of MoS 2 monolayers was carried out by C.P.C. Mechanically-exfoliated devices were prepared by J.J. and D.K. Raman and PL spectroscopy was carried out by C.P.C. and analysed by P.M.. J.J and D.K. carried out EBL to fabricate the FET devices. H.S. assisted with fabrication and wirebonding of devices tested in Peking University (PKU). D.K., J.J. and P.M. carried out the HIM irradiations in Trinity College Dublin (TCD) while J.J and Y.Z. conducted the HIM exposures in PKU. J.J carried out the electrical tests (endurance and potentiation) with assistance from H.S and Y.Z in PKU. P.M. performed FIB processing of irradiated devices and carried out TEM of the cross-sectioned lamellae with assistance from C.D.. D.S.F. carried out helium exposures and TEM imaging of the plan-view irradiated devices after J.J. transferred the samples onto TEM grids. Z.L. oversaw the electrical characterisation work in PKU, while R.Z. and J.X. facilitated microscopy experiments in PKU. N.M and G.S.D. oversaw the material growth process and spectroscopic experiments in TCD. J.J.B. and H.Z. conceived the study and supervised the project. The manuscript was written by J.J., D.K. and P.M. All authors agreed with the final version of the paper.

Time-controlled plasma treatment of MoS2 FETs improves carrier transport due to the presence of a two-dimensional oxide phase.