Abstract
A new theoretical approach to characterize the diffusion of both surface and bulk point defects in crystals is presented. In our model, atomic steps are considered as sources and sinks not only for adatoms and advacancies but also for self-interstitials and bulk vacancies, providing a new mechanism for bulk point defect generation and annihilation. It is shown that the creation and annihilation of self-interstitials and vacancies occur at atomic steps and can be described by introducing a diffusive layer of the bulk point defects adsorbed just below the surface. The atomic step rate of advance is studied taking into account finite permeability of the surface for bulk and surface point defects. The surface permeability results in the appearance of the dependence of the total step rate of advance not only on the supersaturation in vapor phase but also on the supersaturation of point defects in the bulk.
Highlights
Diffusion in crystals and on their surfaces is fundamental to control crystal growth, surface structure, and surface morphology[1,2]
We consider the evolution of the surface morphology of crystal where the two sets of defects meet
We demonstrate the impact of the bulk point defects on the atomic step motion on the crystal surface
Summary
A new theoretical approach to characterize the diffusion of both surface and bulk point defects in crystals is presented. Atomic steps are considered as sources and sinks for adatoms and advacancies and for self-interstitials and bulk vacancies, providing a new mechanism for bulk point defect generation and annihilation. Diffusion in crystals and on their surfaces is fundamental to control crystal growth, surface structure, and surface morphology[1,2] Point defects such as self-interstitials and vacancies in the bulk and adsorbed atoms (adatoms) and surface vacancies (advacancies) at the surface determine the atomic mechanisms of self- and foreign atom diffusion[3,4,5,6,7,8,9,10]. Later BCF theory was extended to the case of the sublimation – reverse process to the crystal growth[12] This required including the surface vacancies to the model and results in appearing the coupling between differential equations describing surface diffusion of adatoms and vacancies. The relationship between surface and bulk processes is not clear and it is difficult to understand whether the surface and bulk exist independently of each other or they have a link which must be accounted in the calculations
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