Manipulation of Color Conversion between Monolayer TMDC and Quantum Dots by Plasmonic Metasurface

• Main Authors: Lin, Chen-An, 林振安
• Other Authors: Kuo, Hao-Chung
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/u8jhsx

碩士 === 國立交通大學 === 光電工程研究所 === 107 === The nano-scale thickness and higher quantum yield compared to other two dimensional materials made transition metal dichalcogenides (TMDCs) a good candidate for realizing ultra-small light emitting devices. However, TMDCs encountered obstacles for practical application since the quantum yields of TMDCs were still relatively low in contrast to traditional semiconductors. Thus, we integrated quantum dots (QDs) with monolayer tungsten diselenide (WSe2), and utilized silver nanodisk (Ag ND) arrays, a kind of plasmonic metasurfaces which could boost absorption and emission at specific resonance frequency, to directly enhance the emission of monolayer WSe2 as well as convert the light from QDs to WSe2. Among the two effects induced by the metasurface, the light conversion or so-called color conversion described the process of one material absorbing the light from other material or source, and then re-emitted the light with absorber’s wavelength, which was a crucial phenomenon used in illumination or display. There were three parts of experiments in the thesis. The first part of experiment will focus on how to realize the Ag ND metasurfaces with desired resonant wavelengths. With the help of FEM simulation as well as bilayer photoresist lift-off process, we designed and fabricated a series of metasurfaces for studying their impact on the color conversion. In the second part, we observed the dependence of plasmonic resonant wavelength. The metasurfaces were made on silica with monolayer WSe2, and their direct enhancement to TMDCs was measured by photoluminescence (PL) system first. Then, we spray coated QDs on them for studying color conversion and found the ideal resonant wavelength located at position between QDs and WSe2 but closer to QDs. At last, we attempted to further increase the conversion efficiency by tuning the metal density of our Ag ND metasurfaces while making all their resonant wavelengths around the ideal position observed in second part. We repeated the measurement in second part and found the density of Ag ND could also affect the enhancement along with conversion efficiency. With higher density came stronger localized surface plasmon effect, which result in the improvement of both effects we got. The successful demonstration of controlling light conversion between QDs and WSe2 through plasmonic metasurfaces suggested that the TMDCs had the potential to be applied to light emitting devices or display technology such as white light emitting diodes (WLEDs) with the assist of localized surface plasmon effect.