Interface bonding of a ferromagnetic/semiconductor junction : a photoemission study of Fe/ZnSe(001)

TL;DR

This study investigates the atomic and electronic structure of the Fe/ZnSe(001) ferromagnetic/semiconductor interface using photoemission techniques, revealing chemical rearrangements and valence-band evolution relevant for tunnel magnetoresistance devices.

Contribution

It provides detailed insights into the interface atomic environment, formation processes, and electronic states of Fe/ZnSe(001), highlighting the chemical and electronic modifications at the interface.

Findings

Fe induces chemical conversion of ZnSe surface layers.

Zn atoms are incorporated into Fe lattice during interface formation.

Fe valence-band states evolve with Fe coverage, affecting tunneling properties.

Abstract

We have probed the interface of a ferromagnetic/semiconductor (FM/SC) heterojunction by a combined high resolution photoemission spectroscopy and x-ray photoelectron diffraction study. Fe/ZnSe(001) is considered as an example of a very low reactivity interface system and it expected to constitute large Tunnel Magnetoresistance devices. We focus on the interface atomic environment, on the microscopic processes of the interface formation and on the iron valence-band. We show that the Fe contact with ZnSe induces a chemical conversion of the ZnSe outermost atomic layers. The main driving force that induces this rearrangement is the requirement for a stable Fe-Se bonding at the interface and a Se monolayer that floats at the Fe growth front. The released Zn atoms are incorporated in substitution in the Fe lattice position. This formation process is independent of the ZnSe surface termination (Zn or Se). The Fe valence-band evolution indicates that the d-states at the Fermi level show up even at submonolayer Fe coverage but that the Fe bulk character is only recovered above 10 monolayers. Indeed, the Fe 1-band states, theoretically predicted to dominate the tunneling conductance of Fe/ZnSe/Fe junctions, are strongly modified at the FM/SC interface.