The cleavage surface of the BaFe_(2-x)Co_(x)As_(2) and Fe_(y)Se_(1-x)Te_(x) superconductors: from diversity to simplicity

TL;DR

This study investigates the surface termination structures of two families of iron-based high-temperature superconductors, revealing diverse surface behaviors in BaFe-based compounds and a simple, consistent surface in FeSeTe compounds.

Contribution

It provides detailed surface structural analysis of BaFe_(2-x)Co_(x)As_(2) and Fe_(y)Se_(1-x)Te_(x) superconductors, highlighting the diversity and simplicity of their cleavage surfaces.

Findings

Ba122 surfaces show complex ordered and disordered structures.

Surface topographies depend on cleavage temperature.

FeSeTe surfaces have a single, tetragonally ordered termination.

Abstract

We elucidate the termination surface of cleaved single crystals of the BaFe_(2-x)Co_(x)As_(2) and Fe_(y)Se_(1-x)Te_(x) families of the high temperature iron based superconductors. By combining scanning tunneling microscopic data with low energy electron diffraction we prove that the termination layer of the Ba122 systems is a remnant of the Ba layer, which exhibits a complex diversity of ordered and disordered structures. The observed surface topographies and their accompanying superstructure reflections in electron diffraction depend on the cleavage temperature. In stark contrast, Fe_(y)Se_(1-x)Te_(x) possesses only a single termination structure - that of the tetragonally ordered Se_(1-x)Te_(x) layer.