Plasmonic nanostructures and their coupling to semiconductor light emitters

• Main Author: Li, Zhenpeng
• Other Authors: Xiong Qihua
• Format: Theses and Dissertations
• Language: English
• Published: 2015
• Subjects: DRNTU::Science::Physics::Optics and light
• Online Access: http://hdl.handle.net/10356/65416
• Institution: Nanyang Technological University

In this thesis, the author presents the work done during the three-year Master’s studies, mainly focusing on the coupling between plasmonic nanostructures and semiconductor light emitters in nanoscale. The first part of my work is studying the coupling between surface plasmon polariton (SPP) and semiconductor nanocrystals, also called quantum dots (QDs). In this work, we fabricated an active semiconductor/dielectric/metal layer-by-layer nanostructure, and we investigated the exciton-SPP coupling in the hybrid nanostructure using steady-state and time-resolved photoluminescence (PL) spectroscopy. According to the experiment result, we found that SPP supported by asfabricated ultra-smooth silver film is strongly coupled to monolayer ensemble CdSeZnS core-shell QDs. The PL intensity of QDs exhibits an overall enhancement while the dielectric spacer layer thickness increases from 0 nm to 45 nm. The PL enhancement factor reaches as large as 26 for the optimal spacer layer thickness of ~ 25 nm. Then we conducted three-dimensional finite domain time difference (FDTD) simulations of electromagnetic field intensity in the same structure, which shows good agreement with our experimental data. The second part of my work is the coupling between SPP and atomically thin transition metal dichalcogenides (TMDs) which show properties of direct band gap semiconductors. In this work, different metallic nanostructure, including nanoparticles, SiO2-shelled nanorod and periodic metallic metamaterials were transferred onto fewlayer Tungsten Selenide (WSe2, a kind of TMDs). Photoconductivity measurements were conducted to study the coupling between SPP and WSe2 thin film. A, B exciton peaks were observed for our WSe2 field-effect transistor (FET) device in temperature dependent photoconductivity spectrum. Further, the WSe2 FET devices were decorated with different metallic nanostructures (gold nanoparticles, gold nanorods and gold nano-arrays imbedded in PDMS film). Based on our experiment result, we found that the photoconductivity properties of the layered WSe2 can be tuned by surface plasmonics. Our results suggest that the coupling between SPP and thin film TMDs is of great significance to application device for photovoltaics and photodetection in atomically scale. All the experiment procedures, results and data analysis about these two projects are stated in the following chapters in this thesis. In addition, a conclusive summary and brief future plan are stated in the end of my thesis.