Dynamic probe of atom exchange during monolayer growth

Abstract

In heteroepitaxy, impinging beam atoms can either wet the surface or swap with substrate atoms. Herein, we present a dynamic study of these phenomena throughout the assembly of the first atomic layer of Ge on Si(111).In situ spectromicroscopic analysis demonstrates that, at a sufficiently high temperature, atom exchange is more significant at the early stages of growth and attenuates as deposition proceeds. Our result highlights the role of propagating monolayer edges in the entropy-driven atom swapping and demonstrates that substitution of Si by Ge is a low-energy pathway to incorporate Ge in the growing monolayer. These observations are confirmed by molecular dynamic simulations.

Tracking atomic processes throughout the formation of heteroepitaxial interfaces

“…The models have either flat surfaces or flat islands or pyramidal QD structures on top. In addition, the Ge/Si mixture is varied on top, especially in the flat island, where some of the prerelaxed structures of are used as start models, too. The SC's used are as follows:…”

“…Figure shows from left to right two SC2b with {111} surfaces and one SC5b structure with a {100} surface. The first SC2b has a flat island on top consisting of solely Ge, the second, with a bilayer island is one of the prerelaxed structures from . The large SC5b has a pyramidal free standing QD on top with {110} facetted and a two‐atomic wetting layer.…”

“…Surface phenomena play a crucial role in defining the nature and the quality of hetero‐epitaxial interfaces and nanostructures, cf., e.g., . Recent morphological and spectroscopic studies combining low energy electron microscopy and x‐ray photoemission electron microscopy of Ge evaporated on Si using molecular beam epitaxy (MBE) demonstrated characteristic temperature dependency of atom exchange processes . It emerges from these studies that the monolayer (ML) growth is nearly abrupt below and at 200 °C indicative of a very limited Ge‐Si exchange at this temperature range.…”

“…With respect to the intermixing of Ge‐Si, the MD with BOP4+ proved that the energy balance of deposited atoms is the reason for our observations providing evidence for the role of the propagating island edges in atoms swapping across the interface. The calculations demonstrated that substitution of Si by Ge is a low‐energy pathway to incorporate Ge in the growing one‐atom‐thick layer . In the present paper, the atomic processes are investigated in detail by extending the minimization towards dynamic deposition simulations.…”

Localized Energy States Induced by Atomic-Level Interfacial Broadening in Heterostructures

“…Interfaces are ubiquitous in design and processing of a variety of low-dimensional systems and devices [1][2][3]. Their characteristic features such as strain field, composition, and topology are known to depart from the idealized picture of atomically flat and abrupt joint surfaces [3][4][5][6]. The nature of these smeared interfaces impacts the behavior of charge carriers and shape the overall optical and electronic characteristics.…”