The laboratory of 2008 Feynman Prize winner (Experimental) James Tour has taken another step toward atomically precise manufacturing with graphene. Sputtering a pattern of zinc atoms on a graphene surface, followed by an acid rinse to remove the zinc, also removes exactly one atomic layer of graphene from where ever the graphene was covered with zinc atoms, forming a pattern on the graphene surface that is atomically precise in the vertical dimension. Resolution in the horizontal dimensions is determined by the mask used to sputter zinc. From physicsworld.com, written by Belle Dumé, “Zinc peels back graphene layers” (requires free registration):
Researchers in the US have succeeded in removing single layers of atoms from graphene for the first time. The technique will be crucial for fabricating high-performance electronic devices from the “wonder material”.
Graphene is a sheet of carbon just one atom thick and is a promising material for making extremely small electronic devices of the future. This is thanks to its unique electronic and mechanical properties that include extremely high electrical conductivity and exceptional strength. However, it is difficult to separate the individual layers of graphene from each other because they tend to stick together. Although ordinary sticky tape can be used to strip off several layers at a time, there is still no reliable way to peel off exactly one layer and certainly not in specific patterns for microelectronic device fabrication.
Now, James Tour and colleagues at Rice University may have overcome this problem by sputtering (or coating) selected areas of the top-most graphene layer in a sample with zinc and then applying hydrochloric acid to the surface as a wash. The technique removes the coated areas of graphene while leaving the uncoated areas and the layers below intact. The process can be repeated to produce multiple patterned layers, say the researchers, or even “chequerboard” structures by removing horizontal and vertical layers to create 3D patterns.
The research was published in Science [abstract, Supporting Online Material]. A podcast interview (transcript) of James Tour is also available. From a Rice University press release written by Mike Williams:
…The Rice lab of chemist James Tour reported this week in the journal Science that sputtering zinc onto multilayered graphene enabled the team to remove a single layer at a time without disturbing the layers beneath.
The discovery could be useful as researchers explore graphene’s electrical properties for new generations of microcircuitry and other graphene-based devices. …
The researchers created a graphene checkerboard by removing horizontal and vertical layers to create a three-dimensional pattern.
They also printed a micro owl, Rice’s mascot, about nine-millionths of a meter wide. …
The researchers were able to create a 100-nanometer line in a sheet of graphene, which suggests the only horizontal limit to the resolution of the process is the resolution of the metal patterning method.
“The next step will be to control the horizontal patterning with similar precision to what we have attained in the vertical dimension,” Tour said. “Then there’s no more room at the bottom at any dimension, at least if we call single atoms our endpoint — which it is, for practical purposes.” …
Whether this advance moves us closer to molecular manufacturing remains to be seen. Even if horizontal atomic resolution is achieved, graphene is essentially a two-dimensional material while proposed nanofactory parts are three-dimensional. However, there seems little doubt that electronic devices and circuitry made from graphene are approaching atomic precision.