Self-organization process in crystalline PbTe/CdTe multilayer structures: Experiment and Monte Carlo simulations

Abstract

Multilayer growth of an immiscible material system is an example of a self-ordering process which results in nanostructures of various patterns. PbTe and CdTe produce an excellent example of an immiscible material system because, despite having nearly the same lattice constants, both components crystallize in different crystal structures - rock salt and zinc blende - respectively. In this report we adjust the kinetic Monte Carlo (kMC) model proposed in our previous publication [1] to the case of PbTe/CdTe multilayer structures formed of ultra-thin PbTe and CdTe layers. The morphology of the multilayers is revealed by transmission electron microscopy (TEM) and the morphological patterns are simulated using the kMC model, which takes into account bulk and surface diffusion. An important factor which determines the morphology of the PbTe/CdTe superlattices is a significant anisotropy of both the surface and the bulk diffusion. The simulations show that the shape, size and dimensionality of the emerging nanostructures strongly depend on the amount of deposited components and the growth rate. Since the amount of the deposited material plays an important role, the desorption process from the surface has to be considered. Our kMC model with adjusted parameters correctly reproduces all morphological details observed in real PbTe/CdTe nanostructures grown with different growth rates and composition ratios. Finally, we show that the growth rate may be used to control morphological transitions between different types of structures of given compositions.