Pressure-Driven One-Dimensional Superlattices in Monolayer Crystals on a Vicinal Surface

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Science

Background:

• Vicinal crystalline surfaces feature periodic atomic steps that can impose superlattices on 2D materials.
• Monolayer transition metal dichalcogenides (TMDs) like WS2 possess unique electronic and optical properties influenced by their crystal symmetry.

Purpose of the Study:

• To investigate the effect of vicinal diamond surfaces on the symmetry of monolayer WS2 under pressure.
• To demonstrate the formation of a 1D superlattice in monolayer WS2 induced by surface steps and external pressure.

Main Methods:

• Utilizing second harmonic generation (SHG) with rotational anisotropy to probe crystal symmetry.
• Comparing the behavior of monolayer WS2 on diamond (230) (vicinal) and diamond (100) (non-vicinal) surfaces.

Main Results:

• Monolayer WS2 on diamond (230) shows orientation-dependent symmetry breaking under pressure, indicative of 1D superlattice formation.
• Monolayer WS2 on diamond (100) largely retains its 3-fold rotational symmetry when pressure is applied.
• Vicinal surfaces enable periodic in-plane modulation of layered crystals.

Conclusions:

• Vicinal surfaces provide a versatile platform for creating 1D superlattices in 2D materials.
• This approach allows for engineering the electronic and optical functionalities of layered crystals through controlled symmetry breaking.