Charge Transfer Dynamics in MoSe₂/hBN/WSe₂ Heterostructures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Interlayer excitons in transition metal dichalcogenide (TMD) heterostructures are crucial for novel quantum phenomena.
• Hexagonal boron nitride (hBN) spacers offer a route to engineer exciton properties and lifetimes.
• Understanding charge transfer dynamics is key to controlling exciton behavior.

Purpose of the Study:

• To experimentally investigate charge transfer dynamics in MoSe2/hBN/WSe2 heterostructures with a 1 nm hBN spacer.
• To quantify the effect of the hBN barrier on charge transfer rates.
• To explore competing processes like exciton-exciton annihilation at high excitation densities.

Main Methods:

• Fabrication of MoSe2/hBN/WSe2 heterostructures with precise hBN layer thickness.
• Time-resolved photoluminescence spectroscopy to probe charge transfer dynamics.
• Varying excitation densities to study nonlinear optical processes.

Main Results:

• Observed hole transfer from MoSe2 to WSe2 through the 1 nm hBN barrier with a slow time constant of 500 ps.
• Demonstrated that hBN spacer dramatically reduces charge transfer speed (over 3 orders of magnitude slower than direct contact).
• Identified strong competition between interlayer charge transfer and intralayer exciton-exciton annihilation at high excitation levels.

Conclusions:

• The hBN spacer provides a powerful tool to significantly slow down interlayer charge transfer in TMD heterostructures.
• This controlled charge transfer facilitates the study and potential application of long-lived interlayer excitons.
• The findings pave the way for designing advanced TMD/hBN/TMD heterostructures for novel optoelectronic devices and quantum studies.