Rhenium Dichalcogenides: Layered Semiconductors with Two Vertical Orientations

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Rhenium and technetium diselenides and disulfides are van der Waals layered semiconductors.
• These materials share similarities with transition metal dichalcogenides (TMDs) but possess lower symmetry.
• Their crystal structure includes only an inversion center, leading to unique layer orientations.

Purpose of the Study:

• To investigate the consequences of lower symmetry in rhenium and technetium disulfides and diselenides.
• To explore the potential for new domain structures in large-area layer growth.
• To establish a method for distinguishing between 'up' and 'down' layer orientations.

Main Methods:

• Production of few-layer ReS2 and ReSe2 samples using micromechanical cleavage.
• Utilizing polarized Raman microscopy to analyze the samples.
• Characterizing the controlled 'up' or 'down' orientations of the layers.

Main Results:

• Demonstrated that layer orientation (up or down) can be controlled during sample preparation.
• Showcased polarized Raman microscopy as a viable technique for differentiating these orientations.
• Confirmed that the lower symmetry leads to symmetrically nonequivalent layer placements on substrates.

Conclusions:

• Polarized Raman microscopy is an essential tool for characterizing large-area layers of these materials.
• The unique symmetry properties offer new possibilities for anisotropic property exploitation in heterostructures.
• Understanding layer orientation is crucial for controlling domain structures in synthesis.