Supercell formation in epitaxial rare-earth ditelluride thin films

TL;DR

This study reports the epitaxial growth of DyTe₂−δ thin films on MgO, revealing supercell formation linked to Te-deficiency and strain effects, with implications for tuning electronic phases in square-net tellurides.

Contribution

It demonstrates the epitaxial growth and structural characterization of DyTe₂−δ films, highlighting supercell formation and strain effects, and provides first principles insights into defect lattice formation.

Findings

Films are single phase and highly oriented.

Supercell diffraction features are observed and linked to Te-deficiency.

First principles calculations explain defect lattice formation due to Fermi surface nesting.

Abstract

Square net tellurides host an array of electronic ground states and commonly exhibit charge-density-wave ordering. Here we report the epitaxy of DyTe$_{2-\delta}$ on atomically flat MgO (001) using molecular beam epitaxy. The films are single phase and highly oriented as evidenced by transmission electron microscopy and X-ray diffraction measurements. Epitaxial strain is evident in films and is relieved as the thickness increases up to a value of approximately 20 unit cells. Diffraction features associated with a supercell in the films are resolved which is coupled with Te-deficiency. First principles calculations attribute the formation of this defect lattice to nesting conditions in the Fermi surface, which produce a periodic occupancy of the conducting Te square-net, and opens a band gap at the chemical potential. This work establishes the groundwork for exploring the role of strain in tuning electronic and structural phases of epitaxial square-net tellurides and related compounds.