Ž . Thin Solid Films 317 1998 6–9 Molecular mechanics simulation of the diamond nucleation and growth ž / ž / on silicon 001 and 111 surfaces R.Q. Zhang a, ) , W.L. Wang b,1 , J. Estevea b , E. Bertran b a Department of Physics and Materials Science, City UniÕersity of Hong Kong, 83 Tat Chee AÕenue, Kowloon, Hong Kong b Departament de Fısica Aplicada i Electronica, UniÕersitat de Barcelona, AÕ. Diagonal 647, Barcelona E08028, Spain ´ ` Abstract Ž . Ž . The nucleations and growths of diamond on silicon 001 and 111 surfaces according to the models previously proposed by us have been simulated in molecular mechanics optimizations for a series of cluster models. These simulations may provide clear mechanisms of the diamond nucleation and growth on such surfaces and further demonstrate that it may be feasible to grow large, single-crystal diamond film. q 1998 Published by Elsevier Science S.A. Keywords: Diamond film; Silicon surfaces; Heteroepitaxy; Interface structure; Modelling 1. Introduction Recently, a number of heteroepitaxial or textured con- tinuous and oriented diamond films on the inexpensive Ž . w x Ž . w x Ž . substrates of Si 100 1–9 , Si 111 4,5,8 and Si 110 w x 10 have been reported. Further efforts are required, how- ever, to achieve single-crystal diamond films, a promising w x electronic material 11–13 , and thus, to reach the final goal. For this purpose, intensive exploration of the nucle- ation mechanism and interface structure is called for. The interfaces of the heteroepitaxial diamond films on Ž . Ž . the Si 001 and 110 substrates have been studied by w x electron microscopy 10,14–17 . It shows that the nucle- ation of diamond could be obtained without the assistance of b-SiC or other conversion layers. Few theoretical ef- forts have been made to investigate the direct growth on silicon, in which atomic models of the interface structure w x have been proposed 17,18 by performing semi-empirical calculations. However, details of a step-by-step deposition must be provided in order to explore the nucleation mecha- nism and confirm the interface structure. We have recently studied the step-by-step nucleation Ž . and growth of diamond on the silicon 001 2 = 1 and Ž . w xw 111 1 = 1 surfaces 19 R.Q. Zhang, W.L. Wang, J. x Esteve, E. Bertran, unpublished . Consequently, interfacial structures in the models for the heteroepitaxial diamond ) Corresponding author. E-mail: APRQZ@cityu.edu.hk 1 Permanent address: Department of Physics, Lanzhou University, Lanzhou 730000, China. ² : film have been found to be in 3:2 lattice match in 110 or ² : 110 direction. However, we also recognized that high nucleation density on a surface which possesses a certain roughness, and the residual mismatch of 1:1.015, remain as difficulties to overcome for a high quality single-crystal diamond film. Nevertheless, it was found in the modelling for a promising growth that the residual mismatch can be Ž . improved on an Si 111 surface. The predicted film is ² : rotated 10.898 around the 111 axis with reference to the silicon substrate, and possesses a very close lateral Ž . atomic-density ratio 1.003:1 to that of natural diamond. We conjecture that this improvement in lattice match is important to achieve single-crystal growth. In this paper, we report the simulation of diamond nucleation and growth according to the proposed models via molecular mechanics. 2. Computational method w x The molecular mechanics 20 method has now become w x a standard tool for chemists 21 . Various schemes and force fields for molecular mechanics calculation have been w x compared 21 . However, most of the available force fields are limited to elements in organic systems. The MM q scheme of HyperChem 2 used in this work is one of the 2 Ž HyperCheme, Release 3 for Windows, Hypercube and Autodesk, . 1993 . 0040-6090r98r$19.00 q 1998 Published by Elsevier Science S.A. All rights reserved.