奈米結構之介面工程邁向高效能光電元件

Abstract

奈米結構因其獨特的電子、光學及催化特性，長期以來備受研究人員關注。為了精準調控這些特性，結構的精密控制至關重要，然而這對於現有的合成方法而言仍是一大挑戰。本論文探討了在奈米結構生長完成後，進一步修飾其性質的相關策略。 首先，我們提出了一種 液對液撞擊技術（liquid-in-liquid impingement technique），能有效增加鈣鈦礦奈米立方體的晶體尺寸。儘管鈣鈦礦奈米立方體展現出強大的光電交互作用與可調控的電子特性，但通常面臨缺陷密度高、結晶性不佳及光電性能退化等問題。現有依賴聚合物基質或熱退火（thermal annealing）的後處理策略，雖能減少奈米立方體表面的負面影響，卻往往需付出高熱預算 的代價，並可能損害成分的完整性。我們的方法則是透過受控的撞擊，經由剪切力驅動的頸縮現象（shear-driven necking）將粒子合併為連續的薄片。顯微鑑定分析證實，其核心機制為燒結作用（sintering）；光譜與電化學測量亦顯示，生成的薄片具有更少的缺陷、更高的穩定性以及更優異的性能。 其次，我們介紹了一種調控二維材料特性的通用方法。透過將「雷射輔助熔鹽合成」與「電化學調控」相結合，有望達成對難熔材料（refractory materials）之相組成、形貌及氧化態的精準控制。我們將此雷射熔鹽平台應用於非凡德瓦力結合的二維固體——氮化鎢之轉化，生成可作為催化劑及功能材料並應用於電子與電化學元件的鎢化合物。這種結合策略為建構具備精密結構與化學屬性的複雜無機化合物，提供了一條強而有力的路徑。

Nanostructures have captured the attention of researchers due to their unique electronic, optical, and catalytic properties. To tailor these properties, precise structural control is required, that has proven challenging for established synthesis approaches. This thesis explores strategies to modify the properties of nanostructures after growth. First, we introduce a liquid in liquid impingement technique that enhances the crystal dimension of perovskite nanocubes. While perovskite nanocubes have demonstrated strong light-matter interaction and tunable electronic properties, they typically suffer from high defect densities, poor crystallinity, and degraded optoelectronic performance. Post-treatment strategies that rely on polymer matrices or thermal annealing have decreased the contribution of nanocube surfaces, but at the cost of high thermal budget and compromised compositional integrity. Our method relies on controlled impingement through shear-driven necking, merging the particles into continuous flakes. Microscopic characterization confirms the occurrence of sintering as the underlying mechanism, and spectroscopic and electrochemical measurements confirm that the resulting flakes possess fewer defects, enhanced stability, and superior performance. Second, we describe a versatile approach to modify the properties of two-dimensional materials. The combination of laser-assisted molten salt synthesis with electrochemical regulation promises precise control over phase composition, morphology, and oxidation state of refractory materials. We apply the laser-molten salt platform to the conversion of tungsten nitride, a non-van-der-Waals 2D solid, to tungsten compounds that can function as catalysts and functional materials for electronic and electrochemical devices. This combined strategy offers a powerful route for engineering complex inorganic compounds with precise structural and chemical attributes.