Title: Tuning of Interlayer Coupling in Large-Area Graphene/WSe2 van der Waals Heterostructure via Ion Irradiation: Optical Evidences and Photonic Applications,
Abstract: Van der Waals (vdW) heterostructures are receiving great attentions due to
their intriguing properties and potentials in many research fields. The flow of
charge carriers in vdW heterostructures can be efficiently rectified by the
inter-layer coupling between neighboring layers, offering a rich collection of
functionalities and a mechanism for designing atomically thin devices.
Nevertheless, non-uniform contact in larger-area heterostructures reduces the
device efficiency. In this work, ion irradiation had been verified as an
efficient technique to enhance the contact and interlayer coupling in the newly
developed graphene/WSe2 hetero-structure with a large area of 10 mm x 10 mm.
During the ion irradiation process, the morphology of monolayer graphene had
been modified, promoting the contact with WSe2. Experimental evidences of the
tunable interlayer electron transfer are displayed by investigation of
photoluminescence and ultrafast absorption of the irradiated heterostructure.
Besides, we have found that in graphene/WSe2 heterostructure, graphene serves
as a fast channel for the photo-excited carriers to relax in WSe2, and the
nonlinear absorption of WSe2 could be effectively tuned by the carrier transfer
process in graphene, enabling specific optical absorption of the
heterostructure in comparison with separated graphene or WSe2. On the basis of
these new findings, by applying the ion beam modified graphene/WSe2
heterostructure as a saturable absorber, Q-switched pulsed lasing with
optimized performance has been realized in a Nd:YAG waveguide cavity. This work
paves the way towards developing novel devices based on large-area
heterostructures by using ion beam irradiation.