Hydrogen adsorption-induced nanomagnetism at the Si(111)-(7$\times$7) surface

TL;DR

This study uses first-principles calculations to show that hydrogen adsorption on Si(111)-(7x7) surfaces induces localized spin polarization and ferrimagnetic orderings, revealing a microscopic mechanism for nanoscale magnetism in semiconductors.

Contribution

It uncovers how hydrogen adsorption induces spin orderings on Si surfaces, providing a microscopic understanding for designing nanoscale magnetic devices.

Findings

H adsorption induces spin polarization of Si dangling bonds.

Charge transfer from rest atoms to adatoms triggers ferrimagnetic order.

H adsorption on rest-atom sites causes Jahn-Teller-like distortions and charge transfer.

Abstract

The creation of magnetism on non-magnetic semiconductor surfaces is of importance for the realization of spintronics devices. Especially, the coupling of electron spins within quantum nanostructures can be utilized for nanomagnetism applications. Here, we demonstrate, based on first-principles density-functional theory calculations, that the adsorption of H atoms on the Si(111)-(7$\times$7) surface induces the spin polarization of surrounding Si dangling bonds (DBs) and their spin orderings. It is revealed that the H adsorption on a rest-atom site exhibits a Jahn-Teller-like distortion that accompanies a charge transfer from the rest atom to the nearest neighboring adatoms. This charge transfer increases the local density of states of such three adatoms at the Fermi level, thereby inducing a Stoner-type instability to produce a ferrimagnetic order of adatom DBs around the adsorbed H atom. Meanwhile, the H adsorption on an adatom site cannot induce spin polarization, but, as adsorbed H atoms increase, the ferrimagnetic order of rest-atom DBs emerges through the charge transfer from rest atoms to adatoms. Our findings provide a microscopic mechanism of the H-induced spin orderings of Si DBs at the atomic scale, which paves a novel way to the design of nanoscale magnetism in the representative semiconductor surface.