Synthesis and Polymorph Manipulation of FeSe<sub>2</sub> Monolayers.

He, Zehao; Poudel, Shiva Prasad; Stolz, Samuel; Wang, Tianye; Rossi, Antonio; Wang, Feng; Mo, Sung-Kwan; Weber-Bargioni, Alexander et al. · Nano Lett · 2024

basic_science · Level V

Where this comes from

Abstract

Polymorph engineering involves the manipulation of material properties through controlled structural modification and is a candidate technique for creating unique two-dimensional transition metal dichalcogenide (TMDC) nanodevices. Despite its promise, polymorph engineering of magnetic TMDC monolayers has not yet been demonstrated. Here we grow FeSe<sub>2</sub> monolayers via molecular beam epitaxy and find that they have great promise for magnetic polymorph engineering. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we find that FeSe<sub>2</sub> monolayers predominantly display a 1T' structural polymorph at 5 K. Application of voltage pulses from an STM tip causes a local, reversible transition from the 1T' phase to the 1T phase. Density functional theory calculations suggest that this single-layer structural phase transition is accompanied by a magnetic transition from an antiferromagnetic to a ferromagnetic configuration. These results open new possibilities for creating functional magnetic devices with TMDC monolayers via polymorph engineering.