The hematite (alpha-Fe_2 O_3) (0001) surface: evidence for domains of distinct chemistry

TL;DR

This study combines theoretical calculations and experimental observations to reveal two distinct surface terminations of hematite (alpha-Fe2O3) (0001), showing significant relaxations and different electronic and magnetic properties depending on environmental conditions.

Contribution

It provides the first combined theoretical and experimental evidence for the coexistence of two chemically distinct hematite (0001) surface domains.

Findings

Two stable surface terminations identified: Fe- and O-terminated.

Significant surface relaxations observed: -57% and -79%.

Coexistence of different surface domains confirmed experimentally.

Abstract

Using spin-density functional theory we investigated various possible structures of the hematite (0001) surface. Depending on the ambient oxygen partial pressure, two geometries are found to be particularly stable under thermal equilibrium: one being terminated by iron and the other by oxygen. Both exhibit huge surface relaxations (-57 % for the Fe- and -79 % for the O-termination) with important consequences for the surface electronic and magnetic properties. With scanning tunneling microscopy we observe two different surface terminations coexisting on single crystalline alpha-Fe_2 O_3 (0001) films, which were prepared in high oxygen pressures.