[论文解读] 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 Applications参考文献 38被引用 3

一句话总结

本研究证明，离子束辐照可通过改变石墨烯的形貌，有效调控大面积石墨烯/WSe2范德华异质结中的层间耦合，增强界面接触并实现可控的电子转移。光学测量显示，其具有可调谐的光致发光和非线性吸收特性，从而在使用辐照后异质结作为可饱和吸收体的Nd:YAG波导腔中实现了优化的Q开关脉冲激光输出。

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.

研究动机与目标

• 解决大面积范德华异质结中层间接触不均匀的问题，该问题限制了器件效率。
• 探索离子辐照作为一种可扩展的方法，用于调控石墨烯/WSe2异质结中的层间耦合并改善界面接触。
• 研究离子辐照后石墨烯/WSe2异质结的光学响应与载流子动力学，以适用于光子学应用。
• 通过将改性异质结用作Q开关激光腔中的可饱和吸收体，展示实际光子器件的集成。

提出的方法

• 对大面积（10 mm × 10 mm）石墨烯/单层WSe2异质结施加离子辐照，以改变其表面形貌并增强界面接触。
• 利用光致发光光谱和超快瞬态吸收测量技术，探测层间电子转移与载流子弛豫动力学。
• 分析在石墨烯存在下WSe2的非线性光学响应，重点关注石墨烯向WSe2的载流子转移效应。
• 在Nd:YAG波导激光腔中引入经离子辐照的石墨烯/WSe2异质结作为可饱和吸收体，实现Q开关脉冲激光输出。

实验结果

研究问题

• RQ1 离子辐照能否有效增强大面积石墨烯/WSe2范德华异质结中的层间耦合与界面接触？
• RQ2 石墨烯的离子诱导形貌改性如何影响异质结的层间电子转移与光学特性？
• RQ3 通过辐照异质结中石墨烯的载流子注入，WSe2的非线性吸收能在多大程度上被调控？
• RQ4 经离子辐照的石墨烯/WSe2异质结能否作为Q开关脉冲激光运行的高效可饱和吸收体？

主要发现

• 离子辐照在单层石墨烯中诱导了形貌变化，显著改善了其与WSe2的界面接触，增强了层间耦合。
• 光致发光测量证实了可调谐的层间电子转移，辐照后发射强度与峰位明显调制。
• 超快吸收动力学揭示，石墨烯为WSe2中光激发载流子提供了快速弛豫通道，降低了复合损失。
• 通过石墨烯向WSe2的载流子转移，有效调控了WSe2的非线性吸收，实现了与各组分不同的选择性光学响应。
• 经离子辐照的石墨烯/WSe2异质结成功在Nd:YAG波导腔中实现了Q开关脉冲激光输出，性能优化。
• 本研究展示了一种可扩展、非破坏性的方法，用于在大面积二维异质结中调控层间耦合，适用于光子器件集成。