Synthesis and Polymorph Manipulation of FeSe₂ Monolayers

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Polymorph engineering offers a route to novel two-dimensional (2D) nanodevices.
• Previous efforts have not achieved polymorph engineering in magnetic transition metal dichalcogenide (TMDC) monolayers.

Purpose of the Study:

• To demonstrate polymorph engineering in magnetic TMDC monolayers.
• To explore the structural and magnetic properties of FeSe2 monolayers.

Main Methods:

• Growing FeSe2 monolayers using molecular beam epitaxy.
• Utilizing scanning tunneling microscopy (STM) and spectroscopy (STS) for characterization.
• Performing density functional theory (DFT) calculations.

Main Results:

• FeSe2 monolayers predominantly exhibit the 1T' structural polymorph at 5 K.
• Voltage pulses from an STM tip induced a reversible transition from the 1T' to the 1T phase.
• The structural phase transition was accompanied by a magnetic transition from antiferromagnetic to ferromagnetic configurations.

Conclusions:

• This study successfully demonstrates polymorph engineering in magnetic TMDC monolayers.
• The findings pave the way for creating functional magnetic nanodevices using TMDC monolayers.
• Controlled manipulation of magnetic and structural phases in 2D materials is achievable.