Atom Control in Electron Microscope
Why it matters
Controlling atoms has been a frontier research field for a long time. The atomic character "IBM" marks the beginning of this effort, and is thriving rapidly thereafter. Being a bottom-up synthetic method, atom-by-atom assembly is an ultimate form of materials tailoring, making it possible for the finest control over the substance in its smallest unit. However, the tool (called scanning tunneling microscope, STM) that is used for making characters of "IBM" requires ultra-low temperature (inside liquid helium) to ensure the stabilization of surface adsorbed atoms.
A variety of atomic dynamics
Controlling atoms has been pursued by people for a long time. From a bottom-up perspective, atom-by-atom assembly is an ultimate form of materials tailoring, making it possible for the finest control over the substance in its smallest unit.
Primary Knock-on Space (PKS)
This is the core concept in the whole work, where the probabilities of different dynamics can be calculated by calculating the areal ratios of the intersection areas between the "ovoid" and the "outcome functions".
Control strategy – Decision tree
The atom control strategy can be determined from a decision tree, where the probability can be calculated through the PKS theory proposed above. The ultimate goal of moving an atom from an initial position to the final position (e.g. from state 1 to state 2 on the right side) will be equivalent to maximizing the branching probabilities between these two transitions (marked in red arrows).
C. Su, M. Tripathi, Q.B. Yan, Z. Wang, Z. Zhang, H. Wang, L. Basile, G. Su, M. Dong, J. Kotakoski,J. Kong, J.C. Idrobo, T. Susi, and J. Li, “Engineering single-atom dynamics with electron irradiation”, Science Advances, 5:eaav2252 (2019).