Tuning the photo-response in monolayer MoS2 by plasmonic nano-antenna.

Jiu Li,Yanfeng Zhang,Saisai Chu,Qingqing Ji,Yan Li,Qihuang Gong,Kebin Shi,Kaihui Liu

doi:10.1038/srep23626

Abstract

Monolayer molybdenum disulfide (MoS2) has recently attracted intense interests due to its remarkable optical properties of valley-selected optical response, strong nonlinear wave mixing and photocurrent/photovoltaic generation and many corresponding potential applications. However, the nature of atomic-thin thickness of monolayer MoS2 leads to inefficient light-matter interactions and thereby hinders its optoelectronic applications. Here we report on the enhanced and controllable photo-response in MoS2 by utilizing surface plasmonic resonance based on metallic nano-antenna with characteristic lateral size of 40 × 80 nm. Our nano-antenna is designed to have one plasmonic resonance in the visible range and can enhance the MoS2 photoluminescence intensity up to 10 folds. The intensity enhancement can be effectively tuned simply by the manipulation of incident light polarization. In addition, we can also control the oscillator strength ratio between exciton and trion states by controlling polarization dependent hot carrier doping in MoS2. Our results demonstrate the possibility in controlling the photo-response in broad two-dimensional materials by well-designed nano-antenna and facilitate its coming optoelectronic applications.

Highlights

Monolayer MoS2 was controllably synthesized on mica through a low-pressure chemical vapor deposition process[25] and transferred onto SiO2/Si substrate
Since the absorbance spectrum of MoS2 is in the visible range, nanostructures with visible wavelength surface plasmonic resonance (SPR) are primarily considered in order to match the absorbance of MoS2 efficiently
We can purposely choose the 532 nm linear-polarized incident laser to efficiently excite the longitudinal mode of nano-antenna SPR without exciting the transverse mode too much

Summary

Introduction

PL (Fig. 1a) and Raman spectra (inset) confirmed the monolayer nature of our MoS2 sample: the PL spectrum shows two peaks related to A exciton at ~ 1.85 eV We employed standard electron beam lithography and pulse laser deposition to fabricate silver nano-antenna patterns on monolayer MoS2 (Fig. 1b). The incident laser polarization has an θ angle relative to the long axis of nano-antennas.

Results

Conclusion