二十面体金刚石和其他五重对称金刚石晶体的生长机制.pdf

Trans. Nonferrous Met. Soc. China 25(2015) 1587−1598 Growth mechanism of icosahedral and other five-fold symmetric diamond crystals 1,2,3 2,3 4 1 Qiu-ping WEI , Li MA , Jun YE , Zhi-ming YU 1. School of Materials Science and Engineering, Central South University, Changsha 410083, China; 2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China; 3. School of Metallurgy and Environment, Central South University, Changsha 410083, China; 4. School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore Received 28 February 2014; accepted 3 December 2014 Abstract: Five-fold symmetric diamond crystals (FSDCs) were synthesized by hot filament chemical vapour deposition (HFCVD) methods. Their surface morphologies and defects were characterised by scanning electron microscopy (SEM). From the perspective of nucleation-growth, a growth mechanism for icosahedral and other five-fold symmetric diamond crystals was discussed. Computer modelling was also carried out. The results show that the dodecahedrane (C20H20) molecule is proposed as a nucleus for the growth of icosahedral diamond crystals (IDCs), wherein the 20 {111} surface planes develop orthogonal to the direction of the original 20 C—H bonds by sequential H abstraction and CH3 addition reactions. IDC can be pictured as an assembly of isosceles tetrahedra, with each tetrahedron contributing a {111} plane to the surface of the IDC and the remainder of the tetrahedral surfaces forming twin planes with neighbouring tetrahedra. The small mismatch (1.44°) between the {111} surfa