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  The mechanism of carbon nanotube and graphene CVD growth  
Dr. Feng Ding:Hong Kong Polytechnic University
    Carbon nanomaterials, such as fullerene, carbon nanotubes (CNT) and graphene have drawn great interests due to their intriguing properties and the unlimited applications. Although the technologies of their synthesizing and using them for many applications have been greatly advanced, their formation mechanisms are still not very clear to us. In this talk, I will address two issues regarding (i) the chirality control in SWCNT growth and (ii) the epitaxy of graphene chemical vapor deposition (CVD) growth.
 
 (i) Encouraged by the dream of synthesizing carbon nanotubes (CNTs) with identical chiral indexes (n,m), the growth mechanism of CNTs has been overwhelming explored both theoretically and experimentally for nearly two decades. By developing a new version of potential energy surface (PES) and a hybridized atomic simulation method, we are able to simulate the nucleation and growth of perfect SWCNTs and the kinetics that controls the chirality assignment in CNT growth has been revealed. Based on this understanding, two strategies that may lead to chirality control in SWCNT synthesis, using high melting solid catalysts and varying the SWCNTĄŻs chirality during growth, are proposed.
 
 (ii) The epitaxial CVD growth on catalyst surface is the most promising method of synthesizing high quality, large area graphene. The key issue that how the orientation of the synthesized graphene is determined is crucial for both experimental design and growth control. Here three modes of graphene CVD growth, on terrace, near metal step, and the embedded growth are proposed and explored by the ab initio method. It is revealed that CVD graphene tends to be embedded on soft catalyst surfaces (e.g., Cu and Au) while the on terrace growth dominates the growth on the rigid catalyst surface (e.g., Ru, Ir, Rh). The graphene grown via on terrace mode may align along with different orientations while the graphene grown via the embedded mode or near metal step mode has only two potential orientations. Based on this understanding, many experimental puzzles are well understood and the strategies of growing high quality graphene on various catalyst surfaces are proposed.
 
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