碳單分子層(graphene)是由碳原子之六角對稱蜂巢狀晶體結構的單層分子膜，因為它的電子被侷限在二維平面裡，其電子的能譜在Brillouim zone 的K 點附近為線性能帶結構(linear dispersion)，所以電子具有無質量Dirac 費米子(massless Dirac fermions)之特性，因此具有特殊的物理性質，是研究量子電動力學或相對論量子現象的理想系統。甚至量化霍爾效應(QHE)也與傳統半導體二維電子氣體之不同。然而graphene 與基板之間因為交互作用，會改變graphene 的電子性質，形成p 型或n 型之導體，但也可能直接影響到graphene 的量子特性，因此了解具有不同分子結構之基板表面，對於graphene 載子的影響是一重要課題。以及研究懸空(suspended)graphene 以了解完全自由的graphene 其真實的性質，也是一值得探討的現象。本計畫將自行製備所有需要的樣品，研究在自組裝單分子膜(self-assembled monolayer)上的graphene 的能帶結構之變化與其中交互作用之機制，以及載子特性與傳輸性質的反應。使用之分析工具有靜電力顯微鏡(electrostatic force microscopy)、micro Raman 光譜術、micro ESCA 能譜術。之後研究懸空graphene 在沒有干擾下之量子干涉現象以及QHE。因為其載子是Dirac fermions，預計會有不同於一般固態材料之量子現象。此工作將分別與日本千葉大學落合勇一教授(量子干涉)及台大梁啟德教授(QHE)合作。落合教授的低溫scanning gate microscopy 將是研究個別disorder 的干涉現象的重要工具。此外也將利用同步輻射中心之掃描式光電子能譜顯微鏡(scanning photo-emission microscopy)研究懸空graphene 之費米能量，以做為了解各種交互作用之能量強度之重要依據。因為將與落合教授合作，本計畫包含一國際合作項目，派人前往千葉大學進行低溫下量子干涉之實驗。 Graphene, a two-dimensional crystal of carbon atoms arranged in honeycomb, has received special attention in recently year due to their remarkable physics properties. Its charge carriers are confined in a two-dimensional plane and it has a linear dispersion, where carriers become massless Dirac fermions at the K point (Dirac point). Therefore graphene possesses very unique physical properties, and is an excellent system to study of quantum electrodynamics and quantum relative phenomena. It is worth noting that the interaction between graphene and the substrate cause significant influence to its electronic properties, such as being p-type or n-type conductors. Also the interaction can become a disturbance to the quantum effect. Therefore, it is an essential issue to understand the interaction with the substrates consisting various molecular structures and their impacts to the electronics. Additionally, the suspended graphene is a good candidate to realize the pure and undisturbed quantum effect. This project will make the graphene samples all by ourselves. We will study the effect of self-assembled monolayers to the energy structure of graphene and the response of the carrier transportation. Electrostatic force microscopy, micro Raman spectroscopy, and micro electron spectroscopy for chemical analysis will be utilized in this study. Then, the quantum interference and quantized Hall effect of the suspended graphene will be studied. The quantum effect of Dirac fermions should remarkably differ from the conventional condensed matters. This portion will collaborate with Prof. Y. Ochiai of Chiba University, Japan (quantum interference) and Prof. C. T. Liang of National Taiwan University (QHE). Prof. Ochiai has a low temperature scanning gate microscopy, which is a power instrument to investigate the influence of individual disorders to quantum interference. The Fermi energy of the suspended graphene is an important reference to understand the strength of the interaction between graphene and other surfaces, so we will study the Fermi energy of suspended graphene with scanning photo-emission microscopy at National Synchrotron Radiation Research Center, Taiwan. In order to conduct the collaboration with Prof. Ochiai at Japan, a subproject of International Collaboration is included in this project.
