Interfacial mixing in heteroepitaxial growth

TL;DR

This paper studies interfacial mixing during heteroepitaxial growth using kinetic Monte Carlo simulations and rate equations, revealing how exchange mechanisms and roughening influence the interdiffusion zone thickness.

Contribution

It introduces a combined simulation and theoretical approach to analyze interfacial mixing and interdiffusion zone formation in heteroepitaxial growth.

Findings

Interdiffusion zone thickness follows a power law decay with distance from the interface.

Exponential cutoff of the power law depends on exchange rates and system size.

Kinetic roughening alters the scaling exponents of interdiffusion.

Abstract

We investigate the growth of a film of some element B on a substrate made of another substrance A in a model of molecular beam epitaxy. A vertical exchange mechanism allows the A-atoms to stay on the growing surface with a certain probability. Using kinetic Monte Carlo simulations as well as scaling arguments, the incorporation of the A's into the growing B-layer is investigated. Moreover we develop a rate equation theory for this process. In the limit of perfect layer-by-layer growth, the density of A-atoms decays in the B-film like the inverse squared distance from the interface. The power law is cut off exponentially at a characteristic thickness of the interdiffusion zone that depends on the rate of exchange of a B-adatom with an A-atom in the surface and on the system size. Kinetic roughening changes the exponents. Then the thickness of the interdiffusion zone is determined by the diffusion length.