Edge-Energy-Driven Growth of Monolayer MnI₂ Islands on Ag(111): High-Resolution Imaging and Theoretical Analysis

Area of Science:

• Surface Science
• Thin Film Growth
• Condensed Matter Physics

Background:

• Reduced dimensionality in transition metal dihalide films offers unique magnetic and electronic properties.
• Precise control over growth conditions is crucial for achieving stoichiometric monolayer islands.

Purpose of the Study:

• To investigate the growth mechanisms of manganese diiodide (MnI2) on a silver (Ag(111)) surface.
• To understand the structural and electronic properties of MnI2 islands formed under specific conditions.

Main Methods:

• Utilized scanning probe microscopy, including Kelvin probe force microscopy, to analyze MnI2 island growth.
• Employed single-crucible evaporation for controlled deposition of MnI2.
• Conducted density functional theory (DFT) calculations to support experimental findings.

Main Results:

• The Ag(111) surface catalyzes MnI2 dehalogenation, forming a reconstructed iodine buffer layer.
• Truncated hexagonal MnI2 islands with alternating edge lengths and distinct Kelvin potentials were observed.
• DFT calculations confirmed island heights, lattice parameters, and revealed asymmetric edge formation energies due to iodine atom positioning.

Conclusions:

• The observed asymmetry in MnI2 island edge lengths is directly linked to differing edge formation energies.
• The specific positioning of edge iodine atoms dictates the structural asymmetry and resulting variations in Kelvin potential.
• This study provides fundamental insights into the controlled growth and property tuning of 2D transition metal dihalides.