Molecular Dynamics Study of High Symmetry Planar Defect Evolution during Growth of CdTe/CdS Films

Abstract

The growth dynamics and evolution of intrinsic stacking faults, lamellar, and double positioning twin grain boundaries were explored using molecular dynamics simulations during the growth of CdTe homoepitaxy and CdTe/CdS heteroepitaxy. Initial substrate structures were created containing either stacking fault or one type of twin grain boundary, and films were subsequently deposited to study the evolution of the underlying defect. Results show that during homoepitaxy the film growth was epitaxial and the substrate's defects propagated into the epilayer, except for the stacking fault case where the defect disappeared after the film thickness increased. In contrast, films grown on heteroepitaxy conditions formed misfit dislocations and grew with a small angle tilt (within ∼5°) of the underlying substrate's orientation to alleviate the lattice mismatch. Grain boundary proliferation was observed in the lamellar and double positioning twin cases. Our study indicates that it is possible to influence the propagation of high symmetry planar defects by selecting a suitable substrate defect configuration, thereby controlling the film defect morphology.

Stabilization and self-passivation of symmetrical grain boundaries by mirror symmetry breaking

“…Even in the previous paper reporting the TEM image of the grain boundary in CdTe, the mirror symmetry seems broken at some layers [23], indicating that the mirror symmetry might be at least partially broken. A recent classical molecular dynamics simulation also found evidence of small rigid body translation for the Cd core structure [30].…”

“…Further atomistic details of grain boundaries can be investigated by Transmission Electron Microscopy (TEM) [19,[22][23][24][25]. Atomistic calculations have been successfully used to construct a three-dimensional atomic structure of grain boundaries from two-dimensional images obtained from TEM experiments [26][27][28][29][30][31][32]. Learning from experimental characterizations of grain boundaries can provide computational models with physically meaningful constraints.…”

Molecular Dynamics Study of Heteroepitaxial Growth of HgCdTe on Perfect and Dislocated (211)B CdZnTe Substrates

“…Previous studies − ,− would increase the thickness of the thermostat region during vapor deposition to maintain a constant temperature throughout the material. This was found to be unnecessary here as the growth rates and incident kinetic energy of vapor atoms used were low enough for the grown MCT to maintain the same temperature as the thermostat region during vapor deposition.…”

“…Numerous molecular dynamics (MD) studies on the crystal growth of semiconductors by vapor deposition have been conducted for various systems. Some examples include growth of microcrystalline and amorphous Si on hydrogen-terminated Si substrates, , InAs/InAs 0.5 Sb 0.5 type-II superlattices on GaSb substrates, homoepitaxy of GaAs, , heteroepitaxy of InGaN on GaN substrates, − and heteroepitaxy of CdTe on CdS substrates. − These studies generally involve varying the conditions of the substrate (temperature, orientation, and presence of defects) and the vapor atoms (velocity, angle, growth rate, and flux ratio between different atom types) and observing their impact on epilayer growth.…”

Elucidating Twinning Mechanisms in CdTe Homoepitaxial Film Growth from Machine Learning Force Field Molecular Dynamics Simulations

“…38−40 Their foundational functional forms restrict the accuracy in complex chemical environments, thereby impeding the precise prediction of growth processes. 3,[28][29][30]41 In this study, we employed the combination of MD and timestamped force-bias Monte Carlo (tfMC) simulations to examine the growth of CdTe films on the single-crystal CdTe substrate. The atomic interactions of CdTe were accurately modeled using our recently developed machine-learning force field (ML-FF).…”