Epitaxially stabilized iron thin films via effective strain relief from steps

TL;DR

This paper demonstrates a novel method to stabilize epitaxial Fe thin films on Cu surfaces using high-density steps as strain relievers, maintaining the metastable fcc structure at greater thicknesses than usual.

Contribution

It introduces a new approach employing surface steps to effectively relieve strain, enabling stabilization of metastable Fe fcc(001) films against bulk phase transformation.

Findings

High-density Cu steps act as strain relievers.

Epitaxial Fe fcc(001) structure maintained at increased thickness.

Electronic properties vary with film thickness and lattice modifications.

Abstract

We show a new way to stabilize epitaxial structures against transforming bulk stable phases for Fe thin films on a vicinal Cu(001) surface. Atomically-resolved observations by scanning tunneling microscopy reveal that high-density Cu steps serve as strain relievers for keeping epitaxially-stabilized Fe fcc(001) lattice even at a transient thickness towards the bulk stable bcc(110) lattice. Spectroscopic measurements further clarify the intrinsic electronic properties of the fcc Fe thin film in real space, implying electronic differences between 6 and 7 monolayer thick films induced by the modification of the lattice constant in the topmost layers.