Comprehensive Optical Band-Edge Characterization for Multilayered MoTe₂ and Its Application in van der Waals-Stacked...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Molybdenum ditelluride (MoTe2) is a 2D material with potential in solar energy and optoelectronics.
• Its band-edge and excitonic transitions require further elucidation for optimized applications.

Purpose of the Study:

• To fully characterize the band-edge and excitonic transitions in multilayered 2H-MoTe2.
• To investigate the thickness-dependent electronic properties of MoTe2.
• To verify theoretical predictions with experimental observations.

Main Methods:

• Micro-thermoreflectance (µTR) spectroscopy to identify excitonic features.
• Thickness-dependent micro-photoluminescence (µPL) measurements.
• Density functional theory (DFT) calculations for band structure analysis.

Main Results:

• Multilayered MoTe2 exhibits multiple excitons (A1s, B1s, A', C, D, E, F, G) and an indirect-gap feature.
• PL emission is thickness-dependent, with optimal intensity at 5 nm (7 layers).
• DFT confirms monolayer MoTe2 as a direct semiconductor, converting to indirect at ~45 layers.

Conclusions:

• The study elucidates MoTe2's excitonic transitions and thickness-dependent electronic properties.
• Experimental results align with DFT calculations, validating the findings.
• A p-SnS/n-MoTe2 heterojunction demonstrates a built-in potential of ~0.62 V, confirming MoTe2's device applicability.