Transient absorption microscopy of monolayer and bulk WSe2

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Optics

Background:

• Tungsten diselenide (WSe2) is a promising 2D material for optoelectronics.
• Understanding exciton dynamics is crucial for device performance.

Purpose of the Study:

• To experimentally investigate and compare exciton dynamics in monolayer and bulk WSe2.
• To determine key parameters like exciton lifetime and diffusion coefficients.

Main Methods:

• Femtosecond transient absorption microscopy was employed.
• A 405 nm pump pulse and a probe pulse at the A-exciton resonance were used.
• Time and space-resolved differential reflection signals were analyzed.

Main Results:

• Ultrafast exciton formation was observed.
• Exciton lifetimes were determined as 18±1 ps (monolayer) and 160±10 ps (bulk).
• Exciton diffusion coefficients were measured as 15±5 cm²/s (monolayer) and 9±3 cm²/s (bulk).

Conclusions:

• Monolayer WSe2 shows significantly faster exciton dynamics compared to bulk.
• Derived parameters are essential for optimizing WSe2-based optoelectronic devices.
• This study provides fundamental insights into exciton behavior in WSe2.