[Paper Review] Tuning of Interlayer Coupling in Large-Area Graphene/WSe2 van der Waals Heterostructure via Ion Irradiation: Optical Evidences and Photonic Applications

Yang Tan, Xiaobiao Liu+5 more|arXiv (Cornell University)|Mar 24, 2017

2D Materials and ApplicationsMaterials Science38 references3 citations

TL;DR

This study demonstrates that ion irradiation effectively tunes interlayer coupling in large-area graphene/WSe2 van der Waals heterostructures by modifying graphene's morphology, enhancing interfacial contact and enabling controlled electron transfer. Optical measurements reveal tunable photoluminescence and nonlinear absorption, leading to optimized Q-switched pulsed lasing in a Nd:YAG waveguide cavity using the irradiated heterostructure as a saturable absorber.

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.

Motivation & Objective

• To address non-uniform interlayer contact in large-area van der Waals heterostructures that limits device efficiency.
• To explore ion irradiation as a scalable method to engineer interlayer coupling and improve interfacial contact in graphene/WSe2 heterostructures.
• To investigate the optical response and carrier dynamics in ion-irradiated graphene/WSe2 heterostructures for photonic applications.
• To demonstrate practical photonic device integration by using the modified heterostructure as a saturable absorber in a Q-switched laser cavity.

Proposed method

• Ion irradiation was applied to large-area (10 mm × 10 mm) monolayer graphene on WSe2 to modify its surface morphology and enhance interfacial contact.
• Photoluminescence spectroscopy and ultrafast transient absorption measurements were used to probe interlayer electron transfer and carrier relaxation dynamics.
• The nonlinear optical response of WSe2 was analyzed in the presence of graphene, focusing on carrier transfer effects from graphene to WSe2.
• A Nd:YAG waveguide laser cavity was implemented with the ion-irradiated graphene/WSe2 heterostructure as a saturable absorber to achieve Q-switched pulsed lasing.

Experimental results

Research questions

• RQ1 Can ion irradiation effectively enhance interlayer coupling and interfacial contact in large-area graphene/WSe2 van der Waals heterostructures?
• RQ2 How does ion-induced modification of graphene influence the interlayer electron transfer and optical properties of the heterostructure?
• RQ3 To what extent can the nonlinear absorption of WSe2 be tuned via carrier injection from graphene in the irradiated heterostructure?
• RQ4 Can the ion-irradiated graphene/WSe2 heterostructure serve as an efficient saturable absorber for Q-switched pulsed laser operation?

Key findings

• Ion irradiation induced morphological changes in monolayer graphene, significantly improving interfacial contact with WSe2 and enhancing interlayer coupling.
• Photoluminescence measurements confirmed tunable interlayer electron transfer, with clear modulation of emission intensity and peak position after irradiation.
• Ultrafast absorption dynamics revealed that graphene acts as a fast relaxation channel for photoexcited carriers in WSe2, reducing recombination losses.
• The nonlinear absorption of WSe2 was effectively modulated by carrier transfer from graphene, enabling selective optical response distinct from individual components.
• The ion-irradiated graphene/WSe2 heterostructure successfully enabled Q-switched pulsed lasing in a Nd:YAG waveguide cavity with optimized performance.
• The study demonstrates a scalable, non-destructive method to engineer interlayer coupling in large-area 2D heterostructures for photonic device integration.