Progress in the study of the dynamic process of graphene doping with single atomic resolution

Progress in the study of the dynamic process of graphene doping with single atomic resolution

Recently, Yang Zhiqing, Associate Researcher of Solid Atomic Image Research Department, Shenyang Institute of Materials Science, Chinese Academy of Sciences Institute of Metals, and Associate Researcher Yin Lichang, Researcher of Advanced Carbon Materials, and others, collaborated with researchers at Oak Ridge National Laboratory, USA, to first use aberration correction. Z-contrast electron microscopy imaging observed the dynamic evolution of graphene topological defect structures, and the dynamic interaction of single Si atoms with topological defects and eventually doping into the microscopic process of graphene, and then using first-principles calculations revealed this The microscopic mechanism of the evolution of an atomic structure.

Direct observation and understanding of the dynamic interaction between a single atom and its surrounding dielectric materials will help people to understand the microscopic evolution of the material structure and predict the formation of new structures, which is of great significance for the development of nano-science and technology.

The researchers found that the 555-777 topological defect on the graphene atom plane has a higher activity and can attract free Si atoms from the neighbors. Z-contrast imaging observed that at the 555-777 topological defect with two Si-substitution atoms, a pair of CC atoms adjacent to Si-Si is still very active, and 90° CC bond rotation occurs continuously.

When the third free Si atom is attracted to the topological defect, it competes fiercely with the active CC atom pair and finally replaces the CC atom pair, forming a trimeric cluster consisting of three Si atoms. cluster.

Under the electron beam, the Si trimer clusters begin to rotate. Theoretical calculations have a rotational energy barrier of about 2.0 eV and a rotational frequency of up to 1012 Hz. Experimental observations also show that the rotating Si cluster and the graphene supporting it are very stable and it is difficult for the electron beam to strike any Si and C atoms at the defect site.

This result is different from the previously reported instability of graphene nanopores, followed by the expansion or healing, indicating that Si modification may be an effective way to stabilize graphene nanopores. Theoretical calculations show that the mechanism of Si-stabilizing graphene nanopores is that the bonding of Si atoms to the dangling bonds C of the graphene nanopores tends to use sp3 hybrid tetrahedral coordination bonding, effectively repelling free C atoms from entering. Graphene planes, which can well stabilize the graphene nanopore structure. Stable graphene nanopores have potential applications in high-resolution DNA sequencing and chemical separation.

The study was funded by the National Natural Science Foundation of China and the National "973" project.

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