Early stage nucleation mechanism for SiC(0001) surface epitaxial growth

Due to the complexity of the binary component system and the difficulty of tracing individual particles in experiments, it is highly desirable to develop simulation tools and models to further reveal the microscopic nucleation behavior of Si and C atoms. In this article, self-consistent rate equations (SCRE) theory combined with the Kinetic Monte Carlo (KMC) model are used to study the nucleation mechanism in the early stage of SiC(0001) surface epitaxial growth under a constant deposition flux. A set of rate equations describing the time evolution of the density of monomers, dimers, and islands are established. By introducing the effective absorption length, the rate equations can be solved self-consistently. In the KMC model, a set of crystal lattices of SiC, including the coordinates of individual Si and C particles and the bond indication, are established. In this model, deposition, adatom diffusion, attachment to and detachment from the clusters of Si or C, and their diffusion along the edge of clusters are considered, and the Hoshen–Kopelman algorithm is implemented to identify and label the clusters. The results show that the time evolution of the density of monomers, dimers, and islands and their dependences on the deposition flux, which are obtained from the SCRE theory, are consistent with the results of the KMC model. The nucleation rate of the dimer increases with the increase in the deposition flux until the number of islands becomes saturated, which leads to a higher density of stable clusters at higher flux. Two regimes governing the absorption length of the monomer are presented. First, before the appearance of the nucleus, the absorption length of the monomer is mainly dominated by monomer density and the diffusion coefficient of adatom. Second, with the growth process, the total capture rate of stable islands gradually plays a dominant role, which is responsible for the further reduction in absorption length and the equal absorption length of Si and C.