Two-dimensional manganese oxide nanolayers on Pd(100): Surface phase diagram

TL;DR

This study maps the complex surface phase diagram of manganese oxide nanolayers on Pd(100), revealing nine novel phases and their dependence on oxygen chemical potential, with implications for epitaxial growth.

Contribution

It provides the first detailed surface phase diagram of MnOx on Pd(100), identifying nine new phases and their structural and oxidation state variations.

Findings

Nine distinct Mn oxide phases identified

Surface phases depend on oxygen chemical potential

Evidence of structurally graded interfaces facilitating MnO growth

Abstract

Two-dimensional manganese oxide layers have been grown on Pd(100) and have been characterized by scanning tunnelling microscopy (STM), low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). The complex surface phase diagram of MnOx on Pd(100) is reported, where nine different novel Mn oxide phases have been detected as a function of the chemical potential of oxygen mO. Three regions of the chemical potential of oxygen can be identified, in which structurally related oxide phases are formed, often in coexistence at the surface. The different regions of mO are reflected in the oxidation states of the respective Mn oxide nanolayers as revealed by the Mn 2p and O 1s XPS binding energies. The MnOx nanolayers form two-dimensional wetting layers and it is speculated that they mediate the epitaxial growth of MnO on Pd(100) by providing structurally graded interfaces.