Strain-Induced Indirect-to-Direct Bandgap Transition, Photoluminescence Enhancement, and Linewidth Reduction in...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) layered materials offer tunable electronic and optical properties via strain.
• Bilayer molybdenum ditelluride (MoTe2) exhibits unique characteristics sensitive to mechanical strain.

Purpose of the Study:

• Investigate the impact of mechanical strain on the photoluminescence (PL) spectral features of bilayer MoTe2.
• Explore strain-induced bandgap transitions and their effect on PL intensity and linewidth.

Main Methods:

• Combined experimental and theoretical approach.
• First-principles electronic band structure calculations.
• Photoluminescence spectroscopy under applied mechanical strain.

Main Results:

• Strain engineering transforms bilayer MoTe2 from an indirect to a direct bandgap material.
• Photoluminescence intensity is enhanced by a factor of 2.24 with increasing strain.
• PL linewidth is reduced by up to 36.6% due to strain-induced excitonic interactions.
• Strain increases the contribution of direct excitons to PL.

Conclusions:

• Strain engineering significantly enhances PL quality and reduces linewidth in bilayer MoTe2, comparable to monolayer.
• The longer emission wavelength of strained bilayer MoTe2 is advantageous for silicon photonics integration.