# Heterogeneous nucleation of pits via step pinning during Si(100) homoepitaxy

## TL;DR

This study uses STM to analyze oxide-induced pits in Si(100) homoepitaxy, revealing that oxide nucleation at step boundaries causes pits, which can be healed by annealing, advancing understanding of surface defect formation.

## Contribution

It presents a new atomistic model for pit nucleation during Si homoepitaxy, linking oxide adsorption at step boundaries to pit formation and dynamics.

## Key findings

- Oxide contamination correlates with pit formation during Si growth.
- Pits are metastable and can be healed by annealing.
- A model for heterogeneous nucleation at step boundaries is proposed.

## Abstract

Using scanning tunneling microscopy (STM), we investigate oxide-induced growth pits in Si thin films deposited by molecular beam epitaxy. In the transition temperature range from 2D adatom islanding to step-flow growth, systematic controlled air leaks into the growth chamber induce pits in the growth surface. We show that pits are also correlated with oxygen-contaminated flux from Si sublimation sources. From a thermodynamic standpoint, multilayer growth pits are unexpected in relaxed homoepitaxial growth, whereas oxidation is a known cause for step pinning, roughening, and faceting on elemental surfaces, both with and without growth flux. Not surprisingly, pits are thermodynamically metastable and heal by annealing to recover a smooth periodic step arrangement. STM reveals new details about the pits' atomistic origins and growth dynamics. We give a model for heterogeneous nucleation of pits by preferential adsorption of {\AA}-sized oxide nuclei at intrinsic growth antiphase boundaries, and subsequent step pinning and bunching around the nuclei.