wafer-scale, with good crystallinity and with contamination levels compatible with large-scale back-end-of-line (BEOL) integration. At present, chemical vapor deposition (CVD) on catalytic copper (Cu) substrates is widely recognized as the most promising route to obtain scalable monolayer graphene for electronic and optoelectronic applications. [1][2][3][4] However, significant hurdles are limiting the actual integration of CVD graphene grown on Cu for most applications. In the first instance, the unavoidable transfer process over wafer-scale is rather cumbersome and introduces contamination, unintentional doping, and mechanical stress, [5][6][7] which adversely impact the physical integrity and electrical performance [8] of the graphene layer. The significant challenge involved in carrying out this seemingly straightforward task is reflected by the vast literature on large-scale transfer processes. Second, metallic contamination levels in transferred CVD graphene grown on Cu are typically well-above the specifications requested for BEOL integration. [6] Clearly, asThe adoption of graphene in electronics, optoelectronics, and photonics is hindered by the difficulty in obtaining high-quality material on technologically relevant substrates, over wafer-scale sizes, and with metal contamination levels compatible with industrial requirements. To date, the direct growth of graphene on insulating substrates has proved to be challenging, usually requiring metal-catalysts or yielding defective graphene. In this work, a metal-free approach implemented in commercially available reactors to obtain high-quality monolayer graphene on c-plane sapphire substrates via chemical vapor deposition is demonstrated. Low energy electron diffraction, low energy electron microscopy, and scanning tunneling microscopy measurements identify the Al-rich reconstruction9° of sapphire to be crucial for obtaining epitaxial graphene. Raman spectroscopy and electrical transport measurements reveal high-quality graphene with mobilities consistently above 2000 cm 2 V −1 s −1 . The process is scaled up to 4 and 6 in. wafers sizes and metal contamination levels are retrieved to be within the limits for back-end-ofline integration. The growth process introduced here establishes a method for the synthesis of wafer-scale graphene films on a technologically viable basis.

We investigated toxicity of 2–3 layered >1 μm sized graphene oxide (GO) and reduced graphene oxide (rGO) in mice following single intratracheal exposure with respect to pulmonary inflammation, acute phase response (biomarker for risk of cardiovascular disease) and genotoxicity. In addition, we assessed exposure levels of particulate matter emitted during production of graphene in a clean room and in a normal industrial environment using chemical vapour deposition. Toxicity was evaluated at day 1, 3, 28 and 90 days (18, 54 and 162 μg/mouse), except for GO exposed mice at day 28 and 90 where only the lowest dose was evaluated. GO induced a strong acute inflammatory response together with a pulmonary (Serum-Amyloid A, Saa3) and hepatic (Saa1) acute phase response. rGO induced less acute, but a constant and prolonged inflammation up to day 90. Lung histopathology showed particle agglomerates at day 90 without signs of fibrosis. In addition, DNA damage in BAL cells was observed across time points and doses for both GO and rGO. In conclusion, pulmonary exposure to GO and rGO induced inflammation, acute phase response and genotoxicity but no fibrosis.

Only a few of the vast range of potential two-dimensional materials (2D) have been isolated or synthesised to date. Typically, 2D materials are discovered by mechanically exfoliating naturally occurring bulk crystals to produce atomically thin layers, after which a material-specific vapour synthesis method must be developed to grow interesting candidates in a scalable manner. Here we show a general approach for synthesising thin layers of two-dimensional binary compounds. We apply the method to obtain high quality, epitaxial MoS 2 films, and extend the principle to the synthesis of a wide range of other materials—both well-known and never-before isolated—including transition metal sulphides, selenides, tellurides, and nitrides. This approach greatly simplifies the synthesis of currently known materials, and provides a general framework for synthesising both predicted and unexpected new 2D compounds.

We demonstrate a simple method for transferring large areas (up to A4-size sheets) of CVD graphene from copper foils onto a target substrate using a commercially available polyvinyl alcohol polymer foil as a carrier substrate and commercial hot-roll office laminator. Through the use of terahertz time-domain spectroscopy and Raman spectroscopy, large-area quantitative optical contrast mapping, and the fabrication and electrical characterization of ∼50 individual centimeter-scale van der Pauw field effect devices, we show a nondestructive technique to transfer large-area graphene with low residual doping that is scalable, economical, reproducible, and easy to use and that results in less doping and transferinduced damage than etching or electrochemical delamination transfers. We show that the copper substrate can be used multiple times with minimal loss of material and no observable reduction in graphene quality. We have additionally demonstrated the transfer of multilayer hexagonal boron nitride from copper and iron foils. Finally, we note that this approach allows graphene to be supplied on stand-alone polymer supports by CVD graphene manufacturers to end users, with the only equipment and consumables required to transfer graphene onto target substrates being a commercial office laminator and water.