Monolayer Borophene Formation on Cu(111) Surface Triggered by Step Edge.

Area of Science:

• Materials Science
• Surface Science
• Condensed Matter Physics

Background:

• Borophene, a 2D material, shows promise for electronics, energy storage, and sensors.
• Monolayer borophene has been grown on Ag(111) and Au(111) via surface adsorption and boron segregation.
• The growth mechanism of borophene on Cu(111) remained unclear.

Purpose of the Study:

• To investigate the growth mode and phase transformation of borophene on Cu(111).
• To understand the formation of β-type borophene on copper surfaces.

Main Methods:

• Utilized scanning tunneling microscopy (STM) for in-situ observation.
• Performed theoretical calculations to support experimental findings.
• Analyzed boron nanostructure evolution under varying substrate temperatures.

Main Results:

• Observed amorphous boron transforming into striped-phase borophene (η = 1/6) at Cu step edges.
• Identified the formation of irregularly shaped β-type borophene (η = 5/36) on the Cu surface or embedded in the Cu layer.
• Striped-phase borophene was identified as a metastable phase requiring further buckling and electron transfer for stabilization.

Conclusions:

• Provided a comprehensive understanding of β-type borophene formation on Cu(111).
• The findings suggest potential pathways for synthesizing borophene on less reactive substrates with 1D defects.