The ultimate control of materials will be to construct, from the ground up, the structure and functionality desired by placing single atoms where we want them. Atomic-scale control of individual atoms would profoundly impact efforts in areas such as quantum computing and semiconductor manufacturing, for example. Not only would this capability be revolutionary with regard to manufacturing exotic materials and devices it would be brought to bear fruitfully on atomic-scale chemistry and our understanding of atomic processes. Being able to stick a few atoms together, controllably, and examine how they bond, what structures they form, and measure the mechanical, optical, and electrical properties is the pinnacle of understanding materials and perfecting material design.
As a starting platform, graphene has emerged as an “ideal” test bed for atomic manipulation in the scanning transmission electron microscope (STEM). While there are practical engineering challenges to overcome, such as how to reliably clean graphene1, 2 and how to introduce the desired materials in a controllable way,3, 4 graphene is robust against a 60 kV electron beam, the position (in x and y) of every atom in the lattice can be directly interpreted from the image (as opposed to a 3D crystal), the atomic species can be determined through image intensity analysis,5 and it is to date the only host material where controllable single atom dopant motion has been demonstrated.6, 7 Here, we practically examine current developments toward atomic scale control of defects in graphene with a STEM beam as a manipulation tool. In particular, we will discuss methodology and mechanisms employed to construct, in situ, atomic-scale structures in graphene with single atoms. Such experiments involve three or four material control paradigms which will also be discussed: Macroscopic sample fabrication and treatment, mesoscopic material transfer and/or in situ material treatments involving the full sample (such as ion deposition or in suit heating), nanoscopic material manipulation in situ (i.e. sputtering with the electron beam in STEM), and, finally, manipulation of single atoms and defects to fabricate a desired structure. While the greatest interest will naturally occur around the manipulation of single atoms, each step in the preparation of a sample conducive to such control is equally important and will be addressed.
1. M. Tripathi et al, physica status solidi (RRL) – Rapid Research Letters 11 (8), 1700124-n/a (2017).
2. O. Dyck et al, arXiv preprint arXiv:1709.00470 (2017).
3. Q. M. Ramasse et al, ACS Nano 6 (5), 4063-4071 (2012).
4. S. Toma et al, 2D Materials 4 (2), 021013 (2017).
5. O. L. Krivanek et al, Nature 464 (7288), 571-574 (2010).
6. T. Susi et al, Ultramicroscopy 180, 163-172 (2017).
7. O. Dyck et al, Applied Physics Letters 111 (11), 113104 (2017).