Issue Date: April 27, 2009
WE ENJOYED the cover article on graphene (C&EN, March 2, page 14). Monolayer graphite (MG) was a term coined by surface scientists for what is now referred to as graphene. MG has been an active and ongoing topic of research in the surface science community for more than 40 years. For example, J. M. Blakely and colleagues worked on the growth of MG on nickel substrates as reported in a series of papers in the 1970s. In 1997 and 1998, inspired by studies of MG by surface scientists, we undertook studies to see if micromechanical exfoliation of graphite—specifically very high quality, highly oriented pyrolytic graphite (HOPG) given to our research group by Arthur Moore of Advanced Ceramics—could yield very thin platelets and perhaps individual layers. In 1999, we published two articles on the topic (Appl. Phys. Lett. 1999, 75, 193; Nanotechnology 1999, 10, 269).
In those years, Rod Ruoff and our team members gave many invited lectures in various venues describing our interest in graphene membranes (using this terminology) and their electrical and mechanical characterization. Indeed, in the Nanotechnology article, we explicitly noted in the "Conclusions" section (quoting verbatim):
"The results of the study show that graphite islands of micrometre size can be fabricated on the HOPG surface in a designed way. The islands can be further manipulated by an AFM tip either in situ as-created on the HOPG surface, or as-transferred on any other flat surfaces, such as a Si(001) surface. Very thin sections of HOPG plates were found on the substrate to which the islands were transferred. The results have the implication that, by using nanofabrication techniques, single or multiple atomic layers of graphite sheets can be fabricated in any desired shape. These graphite sheets are suitable to be used as building elements for new nanostructral materials and nanodevices. Micrometre or nanometre-sized graphene sheets can, in principle, be obtained from the graphite islands created from HOPG, within the size range of current nanofabrication techniques.
"Future work will include trying to obtain graphene rather than multiple-layer thick pieces of graphite, and to understand the physical and chemical properties of graphene and few-layer thick pieces of graphite."
We also note concluding remarks from our article in Applied Physics Letters (quoting verbatim):
"In summary, patterning of freshly cleaved HOPG surfaces was achieved with lithographic preparation of SiO2 mask stops and oxygen-plasma etching. Periodic arrays of micrometer-sized HOPG islands or holes were created on HOPG surfaces. These structures may find applications in graphene origami and are proving useful in studies of the mechanical properties of very thin graphite platelets. ... They may also be used as unique substrates for biological and chemical experiments."
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