二維材料以及超導鐵硒碲傳輸和掃描穿隧式顯微鏡的研究

Abstract

研究員一直以來持續的對各種二維材料以及他們跟不同材料的交互作用有很大的關注，其中二維材料包含了石墨烯、氮化硼、二硫化鉬和層狀氧化物，超導材料為鐵硒碲，本論文展示了我們在這些新穎材料上的傳輸以及掃描穿隧式顯微鏡在低溫以及磁場下研究的成果，最主要的貢獻包含: 第一，藉由利用一層石墨烯去遮蔽帶電雜質以達到上層石墨烯元件特性的改善，第二，研究石墨烯跟二氧化鉬之間隨著外加背電極的相互作用，第三，利用結合傳輸以及掃描穿隧式顯微鏡技術去探討半導體二氧化鉬的特性，並解決了最近在這領域的難題像是有關體二氧化鉬的參雜主要是來自硫的空缺，進一步在單層二氧化鉬元件中觀察到來自二氧化矽表面的參雜效應: 最後，我們試圖用掃描穿隧式顯微鏡去研究石墨烯跟超導鐵硒碲之間的作用，這部分正在持續在進行中。

Researchers have paying intense attention to other two-dimensional (2D) layer crystals such as isolated monolayer graphene and thin-layer crystals of hexagonal boron nitride (hBN), molybdenum disulphide (MoS2), other dichalcogenides, superconductors and combination of them. This thesis presents results of transport and scanning tunneling microscopy (STM) and spectroscopy (STS) experiments on these novel 2D materials and superconductor at low temperatures and in magnetic field. The main findings include that: First, the observation of improvement of graphene device quality by putting another graphene layer underneath. Second, the interaction between graphene and MoS2 as carrier density changed by back gate voltage. Third, we employed scanning tunneling microscopy and spectroscopy combined with gated transport to probe the semiconductor properties of 2H-MoS2. The main conclusions are that n-doping in bulk 2H-MoS2 are caused by S vacancies and the significantly higher doping observed in thin films deposited on SiO2 are likely due to trapped donors SiO2 interface. Finally, we try to study the interaction between graphene and FeSe0.5Te0.5 superconductor by STM and it is still on-going project.