Coarse‐grained approach to amorphous and anisotropic materials in kinetic Monte Carlo thin‐film growth simulations: A case study of TiO₂and ZnO by plasma‐enhanced chemical vapor deposition

Abstract

The growth of TiO 2 and ZnO thin films is studied by means of coarse-grained kinetic Monte Carlo simulations under conditions typically encountered in plasma-enhanced chemical vapor deposition experiments. The basis of our approach is known to work well to simulate the growth of amorphous materials using cubic grids and is extended here to reproduce not only the morphological characteristics and scaling properties of amorphous TiO 2 but also the growth of polycrystalline ZnO with a good approximation, including the evolution of the film texture during growth and its dependence on experimental conditions. The results of the simulations have been compared with available experimental data obtained by X-ray diffraction, analysis of the texture coefficients, atomic force microscopy, and scanning electron microscopy.

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“…To shed light on the mechanisms behind such a complex microstructure and porous network development, we analyze the growth of ZnO by PECVD applying Coarse-grained Monte Carlo simulations. Details on this methodology can be found in a recent reference [48] where we presented the growth of polycrystalline ZnO thin films on flat substrates. In Fig.…”

“…To assist in the analysis of the experimental results, we have made use of kinetic Monte Carlo simulations based on a coarse-grained model developed to simulate the growth of anisotropic crystalline materials (such as ZnO) on surfaces with arbitrary geometries. A detailed description of the model can be found in reference [48]. Here we include a few of the most relevant features: 1) in the first place, the system is defined by a simple 3D cubic lattice with periodic boundary conditions along the directions of the growth plane.…”

“…The activation energy, ΔE l , for a diffusion event is calculated in a simple bond-counting scheme, ΔE l = nE b + mE W + δE, where E b is the bond strength between particles of the film and E W between the film and the substrate. Finally, δE is an extra energy term that accounts for the structural features associated with the specific material being simulated (see details in [48]). For wurtzite, the parameters of this extra term include an anisotropy ratio, A r , that allows adjusting the growth rate of the material in the directions parallel and perpendicular to the c-axis.…”