New progress has been made in the study of the mechanism of epitaxial growth of graphene at the atomic scale in China.
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Recently, Li Zhenyu, a professor at the University of Science and Technology of China, teamed up with colleagues of China University of Science and Technology to make new progress in the mechanism research of graphene epitaxial growth at the atomic scale. It was revealed for the first time that carbon-carbon dimers on different copper substrates are graphene growth. The main carbon supply unit explains the microscopic mechanism determined by different key atomic kinetics in the growth of graphene on different copper substrates, and predicts the different growth morphology (fractal or dense) of graphene on copper surfaces. Phase transition temperature. The research results were published in the "Physical Review Letters" on May 28th. The postdoctoral researcher of the China University of Science and Technology was the first author of the paper.
Epitaxial growth of graphene on a copper substrate by chemical vapor deposition is a widely used method for growing large-area, high-quality single-layer graphene. The quality of graphene samples depends on some key growth parameters, including growth temperature, vapor pressure, substrate morphology, and carbon source. The atomic scale mechanism of graphene epitaxial growth, especially the relative importance of various kinetic processes, is critical to achieve accurate control of graphene non-equilibrium growth.
In different copper substrates, because the geometry of the (111) surface is similar to that of graphene, and the (100) surface is the most widely distributed in the copper foil, these two surfaces have attracted much attention in graphene growth. Experimental studies have shown that graphene growth on copper (111) surfaces is diffusion limited, whereas on copper (100) surfaces the adhesion is limited. When graphene islands are large enough, the formation of branched or dendritic fractal shapes on different surfaces is not the same as forming dense patterns. To date, the understanding of the atomic mechanism of the distinctly different growth behaviors on these two substrates is still lacking. Even the most basic supply unit for the nucleation of graphene is a carbon monomer or a larger carbon polymer, and there is still no clear conclusion.
To address these issues, researchers used a multiscale computational simulation method, combined with first-principles calculations, kinetic Monte Carlo simulations, and rate equation analysis to systematically compare graphene on copper (111) and (100) substrates. The growth kinetics. The results show that on both substrates, the carbon-carbon dimer diffuses faster than the carbon monomer and attaches more easily to the growing graphene island edge. Therefore, the carbon-carbon dimer on the copper substrate is the main supply unit for graphene growth.
In addition, the dimer diffusion barrier on the copper (111) surface is comparable to the attachment energy barrier, while the attachment energy barrier on the copper (100) surface is much larger than the diffusion barrier, resulting in the growth behavior of the graphene showing diffusion limitation and sticking respectively. Attached to the restricted features. At the same time, they also studied the diffusion behavior of carbon-carbon dimers on the edges of graphene islands, which revealed the formation mechanism of different growth forms (fractal or dense) of graphene on different copper substrates, and predicted two The transition temperature of the interphase transformation. This work not only provides a new idea for understanding the atomic mechanism of graphene epitaxial growth on copper (111) and (100) substrates, but also contributes to more precise control of graphene epitaxial growth in device applications.
The above research was funded by the National Natural Science Foundation of China, the Ministry of Science and Technology, the Ministry of Education, and the Chinese Academy of Sciences.
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