Tuning surface metallicity and ferromagnetism by hydrogen adsorption at the polar ZnO(0001) surface

TL;DR

This study uses density functional calculations to show how hydrogen adsorption on ZnO(0001) surfaces can reversibly tune surface metallicity and magnetism, explaining experimental observations and predicting a controllable metal-insulator transition.

Contribution

It demonstrates that hydrogen coverage can reversibly switch surface magnetism and metallicity on ZnO(0001), providing a new method for surface property control.

Findings

Hydrogen adsorption creates a metallic, spin-polarized surface with magnetic moments.

Lower hydrogen coverages lead to insulating surfaces and stronger H-Zn bonds.

The results explain experimental hydrogen adsorption behavior and predict a reversible metal-insulator transition.

Abstract

The adsorption of hydrogen on the polar Zn-ended ZnO(0001) surface has been investigated by density functional {\it ab-initio} calculations. An on top H(1x1) ordered overlayer with genuine H-Zn chemical bonds is shown to be energetically favorable. The H covered surface is metallic and spin-polarized, with a noticeable magnetic moment at the surface region. Lower hydrogen coverages lead to strengthening of the H-Zn bonds, corrugation of the surface layer and to an insulating surface. Our results explain experimental observations of hydrogen adsorption on this surface, and not only predict a metal-insulator transition, but primarily provide a method to reversible switch surface magnetism by varying the hydrogen density on the surface.