Superstructures, Commensurations, and Rotation of Single-Layer TaS₂ on Au(111) Induced by Cs...

Area of Science:

• Materials Science
• Surface Science
• Condensed Matter Physics

Background:

• Two-dimensional materials like tantalum disulfide (TaS2) exhibit unique properties when grown on substrates.
• Understanding the structural evolution and substrate interactions of TaS2 is crucial for its applications.
• Cesium intercalation is a known method to decouple 2D materials from their substrates.

Purpose of the Study:

• To investigate the high-resolution structure of 2D TaS2 on Au(111).
• To study the structural evolution during cesium intercalation and deintercalation.
• To understand the role of H2S atmosphere in the decoupling/recoupling process.

Main Methods:

• In situ synchrotron grazing incidence X-ray diffraction (GIXD).
• In situ synchrotron X-ray reflectivity (XRR).
• Scanning tunneling microscopy (STM) for complementary analysis.

Main Results:

• The initial TaS2 layer is a mixture of TaS2 and S-depleted TaS, forming moiré structures with Au(111).
• Cesium intercalation decouples TaS2, increasing its lattice parameter and lifting it from the substrate.
• Deintercalation, assisted by H2S, leads to stoichiometric TaS2 and improved structural quality, with some flakes rotating by 30° to form new superlattices.

Conclusions:

• Cyclic intercalation/deintercalation in H2S effectively decouples and recouples TaS2, improving its structural quality.
• Cesium intercalation induces significant structural changes, including lattice expansion and flake rotation.
• The study reveals complex moiré patterns and superlattices formed by rotated TaS2 islands, potentially linked to charge density waves.