Large-area grown MoS

摘要

Summary form only given. Monolayer Transition Metal Dichalcogenides (TMDs) have recently attracted great interest in the field of photonics because of their distinctive optical and spin properties. In contrast to bulk TMD materials, which are indirect bandgap semiconductors, monolayer TMDs are highly optically active due to a direct bandgap ranging between 1 and 2 eV [1]. The coupling of TMD excitons to optical fields can be dramatically enhanced by integration with nanophotonic resonators. For instance, enhanced light extraction, signatures of Purcell enhanced emission and even lasing in coupled systems of TMD monolayers transferred onto two-dimensional GaP-based photonic crystal cavities (PCCs) [2,3] as well as microdisk cavities [4] was reported.Here, we demonstrate the integration of chemical vapour deposition (CVD)-grown [5] molybdenum disulphide (MoS2) in one-dimensional, ladder-type PCC patterned in 200 nm thick free-standing SiO2 membranes [6]. For this cavity design, a parabolic modulation of the periodicity confines optical modes in the center of the ladder. These structures were fabricated by conventional electron beam lithography and reactive ion etching. A scanning electron microscope (SEM) image of a typical PCC (before release of the membrane) is shown as an inset in Fig. 1 (a). As shown in the photoluminescence (PL) spectrum in Fig 1 (a), the direct bandgap emission of MoS2 is decorated with three optical modes with quality (Q)-factors exceeding 1700. Figure 1 (b) demonstrates the measured spectral tuning of the different PCC modes (symbols) upon changing the crystal period from 265 nm to 340 nm. The gray lines show the resonance wavelength for membranes predicted by FDTD simulations for membrane thicknesses of d=300 nm (solid) and d=200 nm (dashed-dotted) nicely reproducing the measured data.