二維層狀過渡金屬硫化物於綠能及可撓式電子之應用

Abstract

今日幾乎所有電子元件皆利用三維(3D)半導體為材料，但自從石墨烯(Graphene)於2004年被發現後，電子元件的設計上有了另一種全新的材料選擇：二維(2D)層狀材料，緊接著石墨烯之後，各式二維層狀材料如氮化硼(BN)，二硫化鉬 (MoS2)、二硫化鎢(WS2)、二硒化鉬(MoSe2)、二硒化鎢 (WSe2)，二硒化鈮(NbSe2)亦被發展出來，這些材料因為本身的低維度特性，產生了許多前所未見的載子傳輸、光學、光電、電子自旋、機械結構等性質，為目前物理及材料界積極研究的重要領域，其中過渡金屬硫化物(Transition Metal Dichalcogenides; TMD)因具備適當能隙，特別適合應用於固態電子元件中。但二維層狀TMD是否能取代或互補現有的三維晶體材料，提供電子元件與電路持續微縮的新動能，目前仍未有定論。本計畫希望在「國科會吳大猷先生紀念獎研究計畫」的鼓勵支持下，建立我們團隊在新穎二維層狀TMD於低功耗綠能及可撓式電子元件應用的研究動能，將基礎科學領域發展出的新材料與物理特性，導入固態電子工程領域應用，改善元件特性與功能性。 本計畫規畫以三年的時間投入包含高性能超薄體電晶體、垂直型穿隧式電晶體(TFET)、與可撓式光感應電晶體等重要固態電子元件開發。過去我們的研究團隊在氧化物薄膜電晶體與可撓式電子元件開發上有豐富的經驗，對我們快速進入此全新領域有很大的助益。我們已與中央研究院原子與分子科學研究所李連忠博士所領導的材料合成團隊建立良好的合作夥伴關係，目前成功地在大面積二硫化鉬與二硒化鎢上製作出具良好特性之n型與p型TMD超薄體電晶體，具有高於六個數量級的電流開關比，在此基礎上，我們將系統性地研究如何提升可應用於未來綠能電子中的TMD超薄體電晶體特性。我們也將研究利用TMD異質接面結構的垂直型穿隧式電晶體，期待能較傳統場效電晶體在功耗與性能上皆有所提升。我們也將利用二維層狀TMD適合移轉至任意基板的優點，開發其在可撓式電子，例如光感應式非接觸互動螢幕等應用。

Today almost all electronic devices are made of three-dimensional (3D) semiconductors. However, since the first discovery of graphene in 2004, another new class of materials emerged: two-dimensional (2D) layered material. Various 2D layered materials, such as BN, MoS2, WS2, MoSe2, WSe2, NbSe2, etc. were discovered soon after graphene. Because of the intrinsic low-dimensional characteristics, unprecedented transport, optical, electro-optical, electron spin, and mechanical properties have attracted great attention among the research community of physics and material science. In particular, transition metal dichalcogenides (TMDs) are suitable for the electronic applications because of their moderate bandgap values. However, whether the 2D TMDs can replace or supplement the present 3D semiconductors to continue the device scaling trend is still uncertain. Supported by the NSC Ta-You Wu Memorial Award, this project aims to establish the new research momentum of our team in 2D TMDs focusing on their applications on low-power green electronics and flexible electronics. Leveraging the newly discovered material and physical properties in fundamental science, 2D TMDs will be applied to further improve the performance and functionality of solid-state devices. This three-year project will develop critical solid-state device technology including high-performance ultra-thin body (UTB) FET, vertical tunnel FET (TFET), flexible photo-sensitive FET, etc. In this new research arena, our research team is greatly benefited from our extensive experience in developing oxide-based thin-film transistors and flexible electronics. Furthermore, we have established a mutual cooperation with the 2D TMD synthesis group led by Dr. Lain-Jong Li in the Institute of Atomic and Molecular Sciences, Academia Sinica and successfully fabricated n-type and p-type TMD UTB-FETs with a current on/off ratio greater than six orders of magnitudes on the large-area 2D MoS2 and WSe2, respectively. We will continue improving the characteristics of the TMD UTB devices in a symmetric manner. Additionally, we will investigate the vertical tunnel FET based on the TMD heterogeneous junctions to simultaneously reduce the power consumption and increase device performance as compared with the conventional FET. Utilizing the easy transfer properties of 2D TMDs to arbitrary substrates, we will also explore their new applications on flexible electronics including the photo-sensitive proximity interactive display.