Antiferromagnetic ordering of dangling-bond electrons at the stepped Si(001) surface

TL;DR

This study uses first-principles calculations to demonstrate that antiferromagnetic order can be stabilized at the Si(001) surface step edges, especially when terrace dimers are passivated, revealing quantum size effects.

Contribution

It reveals the possibility of magnetic ordering at silicon surface steps and how passivation and wire length influence this magnetic state, a novel insight into surface magnetism.

Findings

Antiferromagnetic order can be stabilized at Si step edges with passivation.

Jahn-Teller-like distortion is suppressed by hydrogen passivation.

Quantum size effects influence the magnetic ordering energy preference.

Abstract

Using first-principles density-functional calculations, we explore the possibility of magnetic order at the rebonded $D_B$ step of the Si(001) surface. The rebonded $D_B$ step containing threefold coordinated Si atoms can be treated as a one-dimensional dangling-bond (DB) wire along the step edge. We find that Si atoms composing the step edge are displaced up and down alternatively due to Jahn-Teller-like distortion, but, if Si dimers on the terrace are passivated by H atoms, the antiferromagnetic (AFM) order can be stabilized at the step edge with a suppression of Jahn-Teller-like distortion. We also find that the energy preference of AFM order over Jahn-Teller-like distortion is enhanced in an oscillatory way as the length of DB wires decreases, showing the so-called quantum size effects.