Ab Initio Study of the Early Stage of Si Epitaxy on the Chlorinated Si(100) Surface

TL;DR

This study uses density functional theory to explore the initial stages of silicon epitaxy on chlorinated Si(100) surfaces, revealing that silicon incorporation is energetically favorable and chlorine segregates, with implications for quantum device fabrication.

Contribution

It provides the first detailed theoretical analysis of silicon epitaxy on chlorinated Si(100), comparing it to hydrogen resist and highlighting potential advantages for quantum device manufacturing.

Findings

Silicon incorporation under Cl monolayer is energetically favorable.

Chlorine segregates on the surface during silicon deposition.

Silicon clusters can form above the chlorinated surface, with some desorbing and leaving the surface chlorine-free.

Abstract

The homoepitaxial growth of Si on Si(100) covered by a resist mask is a necessary technological step for the fabrication of donor-based quantum devices with scanning tunneling microscope lithography. In the present work, the chlorine monolayer is selected as the resist. Using density functional theory, we investigated the adsorption of a single silicon atom on Si(100)-2$\times$1-Cl as the starting process of Si epitaxy. The incorporation of a silicon atom under a Cl monolayer proved to be the most energetically favorable process. Our results show that chlorine segregates on the surface during Si deposition and does not incorporate into homoepitaxial layers. In addition, we found that SiCl$_2^{\ast}$, SiCl$_3^{\ast}$, and SiCl$_4^{\ast}$ clusters can be formed above a Si(100)-2$\times$1-Cl surface while Si is adsorbed. SiCl$_2^{\ast}$ clusters are bound weakly to the substrate, and their desorption leaves the silicon surface free of chlorine. To check whether the Si epitaxy is possible on the chlorine resist, we compare our results with the well-studied case of a hydrogen resist. We find the two processes to be similar; moreover, epitaxy on chlorine resist appears to have an advantage.