An environmentally benign and scalable route for the production of gram scale quantities of nitrogen-doped graphene using a downstream microwave plasma source is reported. Simultaneous reduction and doping of graphene oxide is achieved and the process negates the need for high temperatures and toxic solvents associated with existing methods. This gas-phase low temperature process is completely dry and, thus, minimises re-aggregation of graphene flakes which is typically associated with liquid phase reduction methods. The resulting material has many potential uses, particularly in electrochemical energy.

Please cite this article in press as: R. Gatensby, et al., Controlled synthesis of transition metal dichalcogenide thin films for electronic applications, Appl. Surf. Sci. (2014) Two dimensional transition metal dichalcogenides (TMDs) are exciting materials for future applications in nanoelectronics, nanophotonics and sensing. In particular, sulfides and selenides of molybdenum (Mo) and tungsten (W) have attracted interest as they possess a band gap, which is important for integration into electronic device structures. However, the low throughput synthesis of high quality TMD thin films has thus far hindered the development of devices, and so a scalable method is required to fully exploit their exceptional properties. Within this work a facile route to the manufacture of devices from MoS 2 and WS 2 , grown by vapour phase sulfurisation of pre-deposited metal layers, is presented. Highly homogenous TMD films are produced over large areas. Fine control over TMD film thickness, down to a few layers, is achieved by modifying the thickness of the pre-deposited metal layer. The films are characterised by Raman spectroscopy, electron microscopy and X-ray photoelectron spectroscopy. The thinnest films exhibit photoluminescence, as predicted for monolayer MoS 2 films, due to confinement in two dimensions. By using shadow mask lithography, films with well-defined geometries were produced and subsequently integrated with standard microprocessing process flows and electrically characterised. In this way, MoS 2 based sensors were produced, displaying sensitivity to NH 3 down to 400 ppb. Our device manufacture is versatile, and is adaptable for future nanoscale (opto-) electronic devices as it is reproducible, cost effective and scalable up to wafer scale.

We report on an adjustable process for chemical vapour deposition of thin films of pyrolytic carbon on inert substrates using an acetylene feedstock. Through modification of the reaction parameters control over film thickness and roughness is attained. These conducting films can be deposited in a conformal fashion, with thicknesses as low as 5 nm and a surface roughness of less than 1 nm. The highly reliable, cost effective and scalable synthesis may have a range of applications in information and communications technology and other areas. Raman and X-ray photoelectron spectroscopies, as well as high resolution transmission electron microscopy are used to investigate the composition and crystallinity of these films. The suitability of these films as electrodes in transparent conductors is assessed through a combination of absorbance and sheet resistance measurements. The films have a resistivity of ~ 2 × 10-5 m but absorb strongly in the visible range. The electrochemical properties of the films are investigated and are seen to undergo a marked improvement following exposure to O 2 or N 2 plasmas, making them of interest as electrochemical electrodes.

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