先進二維材料元件之整合於未來電子技術應用

Abstract

二維材料為其中一類原子級厚度的結構，憑藉著它們許多卓越的性質，例如：不同二維材料種類間之能隙選擇範圍極廣、載子遷移率高、能耗低、無懸鍵、可撓曲性以及高硬度等，使其有潛力成為未來電子學技術發展的核心。為了實際展現並應用這些特性，這篇論文旨在解決以下幾點於該領域關鍵的難題。 首先，生長成的二維材料往往有著極高密度的晶格缺陷，包含了晶界、原子空缺、雜質等等。這些缺陷都會拉低元件的性能效率。為此，我們設計了一種製程來避免這類缺陷。透過薄膜誘導之受抑蝕刻 (FIFE) 這項步驟，我們可以在適合的”檢測用基板”上具象化原子級的缺陷。往後元件的製備便可直接在檢測基板上進行，並且用相應的幾何構型避開這些缺陷。接著，元件可再被轉印到目標的基板上。這套流程不僅提供提升元件表現的可能性，同時也開拓了其發展二維材料穿戴式電子元件的機會。 另外，這篇論文也探索了幾個新穎的元件概念來有效發揮二維材料們的獨特性質。我們展示了簡單的平面憶阻器不僅能在生長用基板上直接置備，還有著對稱、無束縮之遲滯迴圈以及運行穩定性。上述全新的現象可歸因於表面顆粒與硫空缺遷移特徵一致，而這也保證了先進電子元件量產的可能性。最後，我們研究了一個複雜的異質結構元件，該元件以多種二維材料垂直向整合而成。透過其設計面向的優化，我們得以探索在接面處各組件之載子遷移行為。這項技術使我們實現了二維金屬-絕緣層-金屬 (MIM) 電晶體中熱激電子之收集，也點亮了未來發展量產與極快電子學技術之道路

Two-dimensional materials are a class of atomically thin structures, that have great potential to be the basis of future electronics, due to their exceptional properties such as wide choice of the band gap, high mobility, low power consumption, and dangling bond free, flexibility, and robustness. To realize these opportunities of 2D materials, this dissertation is addressing several important challenges. First, as grown 2D material exhibits a high density of lattice defects including grain boundaries, vacancies, impurities, etc. which deteriorate device performance. We devise a fabrication process that can avoid such defects. Through a film-induced frustrated etching (FIFE) step, atomic defects can be visualized on a suitable “detection substrate”. Device fabrication is conducted directly on this substrate, permitting the tailoring of device geometry to avoid defective regions. Finally, the complete device is transferred onto a target substrate. This approach not only provides a route towards enhancing the performance of 2D materials devices but also demonstrates the ability to produce 3D and flexible devices which opens up new opportunities in 2D materials-based wearable electronics Second, several new device concepts are explored to take advantage of the unique properties of 2D materials. We demonstrate a simple lateral memristor fabricated directly on the grown substrate. The devices show a symmetric pinched hysteresis loop and stable operation. The novel phenomenon is ascribed to the migration of surface particles in concert with sulfur vacancies and it provides a route toward scalable fabrication of advanced electronic devices. Finally, we study the fabrication of a complex heterojunction device based on the vertical integration of multiple 2D materials. Through design optimization, we are able to investigate the charge transport in each component of the junction. This platform allows us to demonstrate the hot electron collection in 2D MIM transistors and open up routes for future scalable, ultra-fast electronics.