Investors in business are always concerned about the potential return on investment and this remains as true within the graphene marketplace as it does within any other commercial venture. Before investing individuals and organisations want to know the level of risk and the potential rewards before they commit their money to an enterprise. In the graphene industry there are many unknowns that raise the level of risk but there is one key consideration that could unlock a lifetime of profit.
The race to develop the most efficient, scalable and cost effective method of graphene production is well under way and investing in the most commercial will be what secures the highest profits. Without doubt graphene is a remarkable material and will feature in manufacturing for many years to come, so choosing to invest in the right production company is of crucial importance to any investor. Choose wisely and you will find you have invested in a company whose reputation rises rapidly and who then builds upon their advantage to secure the fortunes of their investors. Choose rashly and your brave investment in innovation may never realise a profit.
To better understand the options open to investors it is probably worthwhile taking some time to investigate the current state of play in production technology. According to an influential overview by Caterina Soldano, Ather Mahmood, and Erik Dujardin of the French Centre, D’Elaboration de Materiaux et d’ Etudes Structurales, graphene production is characterised by four main techniques: mechanical exfoliation, supported growth, the graphene oxide chemical route, and the molecular approach. Each of these techniques is currently used to produce graphene in the laboratory, but which will come to dominate the others and how will the techniques affect other sectors such as mining and product development.
Mechanical exfoliation is the method that won Andre Geim and Kostya Novosolov the Nobel prize and is the method with the longest history. In its simplest form the technology relies upon a shearing force to separate single graphite sheets that are held together by weak Van De Waals forces. Geim and Novoselov’s peculiarly ingenious technique of shearing with sticky tape has been modified over time, largely because of the problem of glue contamination. Most recent attempts suggest a method of graphene adhesion onto insulating substrates using high voltages across fresh cleaved graphite crystals. The graphite crystals and substrate are sandwiched between two electrodes and 1 – 10 kilovolts are passed between them for a couple of seconds. On removal of the graphite monolayer and multilayer graphene samples are found adhered to the substrate.
Micromechanical methods yield the best results in terms of the structural and electrical properties of the graphene produced, largely because of the high quality of the initial crystal. The size of the deposited graphene is also appreciable, however, despite these quality points in its favour, it is unlikely that micromechanical processes will be scalable to industry requirements. For this reason investment in graphite mines that can supply the highest grade of graphite crystal is an investment strategy that needs further consideration.
Supported Growth involves exploiting two different mechanisms of graphene production: thermal decomposition of carbides and chemical vapour deposition. Thermal decomposition of carbides occurring in a vacuum at temperatures of 1300 degrees celsius results in the reorganisation of the carbide surface and the production of graphite and graphene. However, the quality of the graphene produced is variable and better results can be achieved by raising the temperature to 1650 degree celsius and performing the process on silicon carbide in an argon atmosphere. This method results in wafer-scale monolayers with mobility rates only five times less than those of mechanically exfoliated graphene, making large scale processing of graphene devices on SiC wafers a possible commercial venture.
Chemical Vapour Deposition is already championed by CVD Equipment Corporation and involves the decomposition of hydrocarbons on metal catalysing surfaces. The moderate process temperature and large sized graphene crystals that are produced suggest that chemical vapour deposition on metallic surfaces may be the safest option in the manufacture of graphene. However, the strong interaction between the metal and the graphene is cause for some concern, and on a commercial note the process costs remain high whilst the graphene produced is only suitable for low cost, low performance devices.
Graphene Oxide and Wet Chemical Approaches provide a possible alternative for low performance applications where satisfactory electrical and optical properties are required. The chemical approaches are akin to exfoliation methods, however, rather than producing a shearing force to separate the graphene layers chemical approaches rely on weakening the Van De Waals forces by insertion of chemical reactants in the intervening space. Chemical exfoliation is up-scalable and straightforward and therefore its commercial application for large scale production of graphene is entirely possible. However, one problem remains with this process and that is that the reduction step in the chemical process remains incomplete resulting in an ill-defined mix of graphene and graphene oxide. Interestingly, secondary processes derived from this method have produced edge effect graphene nanoribbons with dimensions ranging from 50nm to sub 10nm. Sub 10nm graphene nanoribbions have been shown to be semiconducting.
The molecular approach is characterised by a range of bottom-up techniques that build graphene from carbon precursors of small but well defined size. Thermodynamic conversion of nano diamond clusters has resulted in the production of nano islands, whilst using a core molecule of hexabenzocoronene has produced graphene molecules with as many as 222 carbon atoms in.
So, the advantages and disadvantages, and commercial viability of each method should be much clearer now. What remains is the crystal ball that will decide which of these methods will lead to the most commercially viable production method. Keeping a keen eye on the flow of investment and on the publication of research findings will help investors to better forecast the likely movement of the graphene field, yet, as with every investment, investors in the graphene revolution will never be wholly able to predict the future fortunes of the companies they favour. Due diligence will see you so far but, as the field is newly emerging, there is no real chance of foretelling the direction in which the winds of fortune will blow.