Graphene has attracted a lot of attention in the recent days due to its theoretical transport and mechanical properties. In order to step at the industrial level applications, a solid and reliable production process is needed; up to now the quality of the final product is not able to yield the expected characteristics. Distinction must be made between different products on the market: large domain graphene sheets, which are able to retain most of the physical and electrical properties, and graphene nanosheets or platelets. The latter have drawn a lot of interest due to the ease of manufacture, but are not suitable for the kind of application where graphene properties can really push the limit upwards, one above the others, electronics. The more attractive production methods for large domain graphene nowadays include low pressure chemical vapor deposition, mechanical exfoliation, roll to roll processing and many others. From the industrial point of view, thou, the use of vacuum technology raises excessively the production costs and hence should be avoided. This is the reason why graphene chemical vapor deposition is raising in popularity among many research groups, both for transferring graphene after growth of for using it on the very substrate onto which is grown. Polycrystalline transition metal catalysts are well known systems for obtaining single layer graphene and few layers graphene; among the most used Copper and Nickel are playing an important role because of high level of integration these materials have reached in the integrated circuits technology. Many studies have been carried on understanding the differences that underlie graphene growth mechanisms on these two metals; the more obvious but nonetheless important feature is the different Carbon solubility into the two lattices. That is why, on Copper, graphene grows thanks to surface adsorption and segregation of Carbon atoms, while on Nickel it is needed to exploit Carbon atoms supersaturation: in fact, for Copper, Carbon solubility is negligible while for Nickel it’s roughly 0.2 weight percent at high temperatures. Furthermore, due to metals supports fine structure, the crystallites preferential orientation is known to play a relevant role for copper, where the whole process is mainly involving the surface. On the other side for Nickel and Cobalt the crystals preferential orientation role is less known and almost not taken into account at all. Aim of the present work is to carry on an experimental procedure with the precise intent of exploring the effect of different crystalline structures by electrodeposition both on the final quality of the graphene layer and on the transport phenomena that take place in the metal media. The idea is to describe graphene quality evolution while monitoring metal catalyst properties via inspection techniques like X-ray diffraction, atomic force microscopy and scanning electron microscopy, which can give a deep insight into substrate structure. Graphene quality will be assessed by means of Raman spectroscopy, a very useful method to infer graphene quality via its typical fingerprints.
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Jan 1, 2019
T Heutmann + 1
Open Access
