摘要
在本論文中，我將探討三個奈米材料光學特性相關的主題。我將利用奈米材料本身設計，奈米材料外部結構設計，以及化學處理的方式，使他們的光與物質的相互作用增強。第一個主題是在零維球形奈米殼結構中，利用結構的設計引發耳語廊共振（Whispering gallery mode），藉此提高了奈米材料的光電特性的。通過多個球殼的共振輔助的效果，奈米球殼光偵測器具有全方向探測的效果。此外，偵測速度也因為的納米殼之間的交界處障礙的存在而有所提升（響應/恢復時間：0.8 / 0.7毫秒）。第二個主題是利用機板的設計來調變二維材料的光耦合特性。為了要能使二維材料能有更佳的光電元件運用，徹底了解二維材料的光耦合機制與其周圍介電材料的控制是我們的首要任務。由於二維材料只有原子尺度的厚度，其周圍環境，如基板，可以大幅的影響其發光或散射光的放光效率。這個工作中，我們藉由實驗，理論，及模擬的結果詳盡的探討基板厚度對二維材料光耦合效率的關係。利用特殊的厚度我們可以將光激發光的效率增強11倍，拉曼散射光的效率增強30倍。此外，藉由基板的設計選區蝕刻，我們可以控制二維材料發光的區域。第三個主題是利用化學處理方式，修補二維材料的缺陷藉此提升材料的光致發光量子產率。二維材料中最熱門的二硫化鉬其光致發光量子效率僅有0.6％，原因是這個材料在生成之後其缺陷密度很高。我用有機強酸的處理方式，將缺陷導致的非輻射複合消除，最終將二維材料的量子效率提升超過兩個數量級，達到超過95％的最終量子效率。這工作實現了完美單層二維材料。我們預期這個工作將對未來二維材料發光二極管，雷射，太陽能電池，光子晶體的設計及發展有重要影響。
並列摘要
In this thesis, I will experimentally explore three topics which realize the improvement of photonic properties of nanomaterials and enable their light-matter interaction. The first topic is the optical resonance in zero-dimensional spherical nanoshell structures, where the excited whispering gallery mode (WGM) resonance significantly enhances the optoelectronic properties of the nanomaterial. Due to the resonance-assisted effect by the multiple convex shells, the nanoshell devices show enhanced optoelectronic performance and omnidirectional detectability both for incident angle and light polarizations. In addition, response and recovery speed are promoted (response/recovery times: 0.8/0.7 ms) because of the existence of junction barriers between nanoshells. The second topic is the engineering of light outcoupling in two-dimensional (2D) materials. When light is incident on 2D transition metal dichalcogenides (TMDCs), it engages in multiple reflections within underlying substrates, producing interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Here I present a simple method to engineer the light outcoupling in semiconducting TMDCs by modulating their dielectric surroundings. We show that by modulating the thicknesses of underlying substrates and capping layers, the interference caused by substrate can significantly enhance the light absorption and emission of WSe2, resulting in a ~30 times increase in Raman signal and a ~11 times increase in the photoluminescence (PL) intensity of WSe2. Based on the interference model, we also propose a strategy to control the photonic and optoelectronic properties of thin-layer WSe2. The third topic is to enhance the photoluminescence quantum yield of 2D materials. The prototypical 2D material, MoS2 is reported to have a maximum quantum yield of 0.6% which indicates a considerable defects density. I present an air-stable solution based chemical treatment by an organic superacid which uniformly enhances the photoluminescence and minority carrier lifetime of MoS2 monolayers by over two orders of magnitude. The treatment eliminates defect-mediated non-radiative recombination, thus resulting in a final quantum yield of over 95% with a longest observed lifetime of 10.8±0.6 ns. Obtaining a perfect optoelectronic monolayer opens the door for light emitting diodes, lasers, and solar cells based on 2D materials.
參考文獻
延伸閱讀
- Chen, T. T. (2008). 奈米半導體材料之光電性質研究 [doctoral dissertation, National Taiwan University]. Airiti Library. https://doi.org/10.6342/NTU.2008.00329
- 彭成彰（2014）。奈米射出成形技術及光學特性研究〔碩士論文，國立中央大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0031-0412201511595577
- 劉沂欣（2021）。奈米材料在光電磁學之應用。化學，79(4)，283-284。https://doi.org/10.6623/chem.202112_79(4).013
- Nguyen, H. P. T., Arafin, S., Piao, J., & Cuong, T. V. (2016). Nanostructured Optoelectronics: Materials and Devices. Journal of Nanomaterials, 2016(), 372-373-037. https://doi.org/10.1155/2016/2051908
- Yatsui, T., Jagadish, C., & Lerondel, G. (2015). Nanophotonics: Fabrications and Application of Nanoscale Optics to Novel Photonic Devices. Advances in Optical Technologies, (2015), f1-1. https://doi.org/10.1155/2015/609682