World’s thinnest pane of glass unveiled
Semi-accidental discovery made during the experimental production of graphene
A paper in 1932 by William Holder Zachariasen hinted at the atomic structure of glass, which at the time was unexplored. This deduction was based purely on the properties of glass known at the time. For example, the fact it does not have a crystalline structure indicated that molecules within it are not symmetric.
This work now appears to be vindicated following new research reported in Nano Letters, which shows that a 2D layer of glass imaged using Transmission Electron Microscopy (TEM) has an extremely similar structure to that deduced in the 1932 work.
As with many scientific discoveries, this one was partially accidental. The team intended to make graphene for an experiment; however, unintended consequences actually resulted in graphene with a layer of glass forming instead. The researchers suspect that this is due to air leaking into the process.
Conventional glass (as found in windows) is made of silicon dioxide – also known as silica. The process used to create the graphene, in this instance, involved a quartz substrate on carbon. When air leaked into the process, this caused the carbon to be oxidised (and the quartz subsequently reduced). This forms silica in the same structure of glass – yet just three atoms thick, making it effectively 2D.
This research is important for two reasons. The first of these is to allow direct imaging of molecules, some of which may not occur naturally. The other reason is that it opens the door to synthesising a wide variety of other 2D molecules through the use of a graphene substrate: it may be possible to produce a glass from aluminium oxide with this technique. Additionally the graphene support removes the need for the variety of conditions that 2D materials need to form, such as unreactivity.
This provided an opportunity to investigate the properties of the rings within glass. One of the properties discovered was that the glass was not covalently bonded to the graphene – this would cause an unacceptable amount of strain within the molecule. This can be seen in graphical models, which show a large mismatch between the lattice of graphene and the glass.
Instead, the van der Waals interactions cause the attraction to occur, resulting in a stabilisation effect within the glass. This shows that graphene could be a core component of production of new 2D substances.
As for the 2D silica-based glass, this could have a use in electronics, namely semiconductors, or as gate insulators in semiconductors. This is thanks to the ease of which the graphene and glass can be stripped from the starting copper.
