以氮化物電漿子材料異質結構增強二維材料之光與物質交互作用之研究

Abstract

二維材料因具有原子級厚度、弱介電屏蔽效應與強庫倫交互作用，使其展現出高於傳統半導體的激子束縛能，並可在室溫下維持穩定的激子態，因此已成為研究奈米尺度光與物質交互作用的重要平台。特別是過渡金屬二硫族化物具有直接能隙、強激子響應、自旋–谷自由度與可閘極調控之光電特性，使其在極化子、光偵測、發光元件與量子光電應用中展現高度潛力。然而，二維材料的原子級厚度亦限制了其與自由空間光場之耦合強度，進而影響光吸收、發光效率與主動調控能力。過去文獻常利用機械剝離法製作二維材料樣品做研究，雖具有良好材料品質，但尺寸有限，難以作為大面積元件應用；為克服此問題，本論文以CVD成長晶圓級單晶二維材料為基礎並結合開放式共振平台及過渡金屬氮化物電漿子共振平台，系統性增強僅三個原子層厚之二維材料中的光與物質交互作用。 本論文共分為六章。第一章介紹本研究之背景與動機，說明晶圓級二維異質結構、過渡金屬二硫族化物、過渡金屬氮化物，以及激子–極化子、雙曲極化激元與三重子等相關物理概念。此章節建立本論文的核心問題：如何在不破壞二維材料本徵電子結構的前提下，透過異質結構、共振腔與介面工程，增強其光場侷限、激子耦合與主動調控能力。第二章說明本論文所使用之實驗方法與量測原理，包含瞬態吸收光譜、低溫共焦光激發螢光系統、探針台結合共焦螢光量測系統、穿透／反射光譜與電性量測整合系統、橢圓偏振光譜量測，以及高真空射頻磁控濺鍍系統成長導電之過渡金屬氮化物。這些實驗方法共同支撐後續對材料光學性質、超快載子動力學、介面電性調控與過渡金屬氮化物薄膜特性的系統性分析。第三章探討晶圓級單層二硫化鎢與氧化鋁所構成之多層異質結構中的強光–物質交互作用。本研究利用 WS2/Al2O3 超晶格結構，使單層 WS2 激子與波導模態有效耦合，成功觀察到可調控之激子–極化子行為。透過角解析反射光譜與理論模擬，可確認上、下極化子分支之形成；進一步利用時間解析瞬態吸收光譜，揭示極化子態之生命週期變化與超快載子動力學。研究結果顯示，強耦合可有效改變二維材料中的能量弛豫途徑，並於皮秒尺度下觀察到由非線性能量轉移所引發之極化子態間粒子數反轉行為。此結果說明，晶圓級二維材料異質結構可作為發展極化子型超快調變器、光開關與相位調控元件之潛在平台。 第四章進一步發展以過渡金屬氮化物為核心之雙曲光學異質結構。本研究以氮化鈦與六方氮化硼建構多層混維異質結構，利用氮化鈦之光學金屬特性與六方氮化硼之凡德瓦介面特性，使該結構於可見光至紅外波段展現雙曲色散行為。相較於傳統由金、銀等貴金屬所構成之雙曲材料，氮化鈦具備較佳之熱穩定性與製程相容性。此外，氮化鈦與六方氮化硼所形成之凡德瓦介面不具有懸空鍵，可有效抑制高溫下跨介面原子擴散，使其在高溫與高壓環境中仍能維持雙曲色散特性。相較之下，以氧化鋁作為介電層之 TiN/Al2O3 超晶格在高溫退火後呈現較明顯的光學性質劣化。此結果證明，透過凡德瓦介面工程可有效提升過渡金屬氮化物雙曲材料的熱穩定性，並為高穩定性奈米光子、熱輻射調控與極端環境光學元件提供新的材料平台。第五章探討氮化鉿閘極與晶圓級單層二硫化鉬所構成之異質介面，並進一步發展可主動調控之二維發光平台。本研究利用 HfN/Al2O3/MoS2 異質結構，藉由氮化鉿與單層 MoS2 之間適當的功函數匹配，引發能帶彎曲並促進介面載子累積，進而增強對激子與三重子發光的靜電調控能力。實驗結果顯示，其發光調製率可達 24%，約為傳統矽基閘極結構的五倍，且可調控面積超過 5000 μm2。為進一步提升發光效率，本研究引入電漿子奈米共振腔，透過奈米粒子於金屬薄膜上所形成之隙電漿子共振與珀塞爾效應，實現約 46 倍之發光增強，同時保有閘極可調之主動調控特性。此結果證明，過渡金屬氮化物不僅可作為與二維材料整合之穩定導電閘極材料，亦可進一步結合電漿子奈米結構，發展兼具室溫操作、大面積可調控與 CMOS 相容性的二維發光元件平台。 第六章總結本論文之主要研究成果，並提出未來發展方向。本論文證明，透過晶圓級二維材料、過渡金屬氮化物與異質結構設計之整合，可從光場侷限、介面耦合、雙曲色散與主動電性調控等不同層面，有效提升二維材料中的光與物質交互作用。未來可進一步將此材料平台延伸至晶片整合奈米光子元件、可調式極化激元元件、紅外光偵測、熱輻射控制與量子光電應用。整體而言，本論文建立了一套以過渡金屬氮化物電漿子材料為核心之二維材料異質整合策略，不僅深化了二維材料與陶瓷電漿子材料之基礎物理理解，也為大面積二維光電元件、激子極化子平台與 CMOS 相容奈米光子元件之發展開拓新的方向。

Two-dimensional (2D) materials, owing to their atomic-scale thickness, weak dielectric screening, and strong Coulomb interactions, exhibit exciton binding energies higher than those of conventional semiconductors and can maintain stable excitonic states at room temperature. They have therefore become an important platform for studying nanoscale light–matter interactions. In particular, transition metal dichalcogenides (TMDC) possess direct bandgaps, strong excitonic responses, spin–valley degrees of freedom, and gate-tunable optoelectronic properties, making them promising for polaritons, photodetection, light-emitting devices, and quantum optoelectronic. However, their atomic-scale thickness also limits their coupling strength with free-space optical fields, thereby restricting optical absorption, emission efficiency, and active tunability. Previous studies have commonly relied on mechanically exfoliated 2D materials, which offer high quality but limited size and are therefore difficult to apply to large-area devices. To overcome this limitation, this dissertation uses CVD-grown wafer-scale single-crystalline 2D materials and integrates them with open-cavity resonant platforms and transition metal nitride (TMN) plasmonic resonant platforms to systematically enhance light–matter interactions in atomically thin 2D materials. This dissertation consists of six chapters. Chapter 1 introduces the background and motivation of this research, including wafer-scale 2D heterostructures, TMDC, TMN, and the relevant physical concepts of exciton–polaritons, hyperbolic polaritons, and trions. This chapter establishes the central question of the dissertation: how to enhance optical-field confinement, exciton coupling, and active tunability through heterostructure design, resonant cavities, and interface engineering, without disrupting the intrinsic electronic structure of 2D materials. Chapter 2 describes the experimental methods used in this dissertation, including TAS, low-temperature PL, probe-station-based PL, integrated transmission/reflection spectroscopy with electrical measurements, spectroscopic ellipsometry, and the customized sputtering system for plasmonic TMN growth. These methods support the analysis of optical properties, ultrafast carrier dynamics, interfacial electrical modulation, and TMN thin-film characteristics. Chapter 3 investigates strong light–matter interactions in multilayer heterostructures composed of wafer-scale monolayer WS2 and Al2O3. A WS2/Al2O3 superlattice is used to couple monolayer WS2 excitons with waveguide modes, enabling tunable exciton–polariton behavior. Angle-resolved reflectance spectroscopy and theoretical simulations confirm the formation of upper and lower polariton branches. Time-resolved TAS further reveals the lifetime evolution and ultrafast carrier dynamics of polaritonic states. The results show that strong coupling modifies energy relaxation pathways in 2D materials, and that nonlinear energy transfer can induce population inversion between polariton states on the picosecond timescale. These findings indicate that wafer-scale 2D heterostructures can serve as a potential platform for polariton-based ultrafast devices. Chapter 4 develops hyperbolic optical heterostructures based on TMN. Multilayer mixed-dimensional heterostructures are constructed using titanium nitride (TiN) and hexagonal boron nitride (hBN). By combining the optical metallicity of TiN with the van der Waals (vdW) interfacial properties of hBN, the resulting structures exhibit hyperbolic dispersion from the visible to the infrared spectral range. Compared with noble-metal-based hyperbolic materials, TiN offers better thermal stability and process compatibility. In addition, the dangling-bond-free vdW interface between TiN and hBN suppresses atomic diffusion at elevated temperatures, allowing the hyperbolic dispersion to be preserved under high-temperature and high-pressure environments. In contrast, TiN/Al2O3 superlattices show more pronounced degradation in optical properties after high-temperature annealing. These results demonstrate that vdW interface engineering can improve the thermal stability of TMN-based hyperbolic materials and provide a robust platform for nanophotonics, thermal-radiation control, and optical devices operating in extreme environments. Chapter 5 explores the heterointerface between a hafnium nitride (HfN) gate and wafer-scale monolayer MoS2, and further develops an actively tunable 2D light-emitting platform. In the HfN/Al2O3/MoS2 heterostructure, the work-function matching between HfN and monolayer MoS2 induces band bending and promotes interfacial charge accumulation. This, in turn, enhances the electrostatic modulation of exciton and trion emission. The experimental results show that the PL modulation depth reaches 24%, approximately five times higher than that of conventional Si-based gate structures, while the tunable area exceeds 5000 μm2. To further improve the emission efficiency, a plasmonic nanocavity is introduced. Through NPoM cavity and the Purcell effect, an approximately 46-fold emission enhancement is achieved while maintaining gate-tunable active control. These results demonstrate that TMN can serve not only as stable conductive gates for 2D materials, but also as plasmonic platforms for room-temperature, large-area, tunable, and CMOS-compatible 2D light-emitting devices. Chapter 6 summarizes the main findings and discusses future directions. This dissertation demonstrates that, through the integration of wafer-scale 2D materials, TMN, and heterostructure design, light–matter interactions in 2D materials can be enhanced through optical-field confinement, interfacial coupling, hyperbolic dispersion, and active electrical modulation. Overall, this dissertation establishes a 2D-material heterointegration strategy centered on TMN plasmonic materials, deepens the physical understanding of 2D materials integrated with ceramic plasmonic materials, and opens new directions for large-area 2D optoelectronic devices.