We have developed a Kinetic Monte Carlo (KMC) code adapted to the homoepitaxial growth of MgO. The KMC approach is an efficient tool for modeling a complex sequence of simple events. The events, which form the growth of the oxide, are the followings: deposition, various diffusion mechanisms, evaporation and chemical reactions. These events and their probabilities obtained from their frequencies are the input data of the KMC simulations. We have used ab initio calculations (Density Fonctional Theory) at T=0 K [1] and Molecular Dynamics (MD) computations based upon phenomenological potentials at T=1000 K [2] to guess and discover the possible events occurring and their corresponding frequencies.
KMC allows us to bridge the time scale gap between diffusion events (nanoseconds) and deposition events (seconds). Our KMC code simulate the homoepitaxial growth by Molecular Beam Epitaxy. The simulations where carried out on a MgO(001) monocrystalline substrate using a cell with periodic boundary conditions. The dimensions of the system can reach a few hundred thousand of molecules.
We simulated the MgO homoepitaxial growth at different temperatures and pressures of the molecular beam and at a chosen roughness of the MgO substrate. We investigated and compared the effects of each event in order to estimate the role of diffusion in crystal growth and the contributionof every diffusion mechanism. To obtain a realistic model, we varied the event probabilities as a function of the neighboring of the migrating molecule: near defects (steps, vacancies) and centers of nucleation (clusters). We have also used MD as a tool to check the validity of some hypothesis made within KMC.

[1] G. Geneste, J. Morillo, F. Finocchi, Appl. Surf. Sci. 188 (2002) 122.

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