為 了 了 解 鐵 磁 性 物 質 Co 長 在 graphene/Pt(111) 上 的 磁 特 性 ， 本 實 驗 先 在 Pt(111) 上製備 graphene，而後在 graphene 上鍍上鐵磁物質 Co，形成 Co/graphene/Pt(111)。在超高真空腔中，我們使用高溫退火 (annealing) 的方式製備 graphene，使碳原子在 Pt(111) 晶體中析出 (segregate) 到晶體表面，而形成
graphene。使用掃描試穿隧電子顯微鏡 (Scanning Tunneling Microscopy，STM) 及低能量電子繞射儀 (Low Election Energy Diffraction，LEED) 確認 graphene
成長在 Pt(111) 上的特性。接著，在低溫 (約 200 K) 下，使用電子束蒸鍍鎗 (Electron Beam Evaporator) 蒸鍍 3 到 25 ML 的 Co 在 graphene/Pt(111) 上，透過 X 射線磁圓偏振二向性 (X-ray magnetic circular dichroism，XMCD) 的量測，得知不同厚度 Co/graphene/Pt(111) 的鐵磁特性，且利用 STM 觀察少數層
Co/graphene/Pt(111) 的成長行為。經由一系列的研究與分析後，我們從 X 光吸收能譜中發現，大於 15 ML Co/graphene/Pt(111) 具有鐵磁訊號，而在少數層的
Co/graphene/Pt(111) 時，並不具有鐵磁特性。觀察 STM 的影像，顯示少數層 (<3 ML) Co 在 graphene 上呈現顆粒的形態。

In this study, we aimed to investigate the magnetic properties of the Co/graphene/Pt(111). Firstly, we used the annealing technique to prepare graphene. The car-
bon atoms were segregated from the bulk of the Pt(111) to form graphene eager on the surface. After the preparation of graphene, we con&#64257;rmed its quality
by using STM and LEED. Secondly, we deposited 3 to 25 ML (monolayer) Co on graphene/Pt(111) by electron beam evaporator at low temperature ( 200 K). Then, we measured the ferromagnetic properties of different thickness of Co on graphene / Pt(111) by XMCD, and studied the growth behavior of few monolayer Co on graphene by STM. By serial analysis no ferromagnetic property of few monolayer Co was detected on graphene / Pt(111) by X-ray absorption spectra. The STM image show that the few monolayer Co on graphene mucleates as clusters.

1 簡介 1
2 原理及性質 3
2.1 石墨烯 (Graphene) 介紹 . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1 Graphene 的晶格結構 . . . . . . . . . . . . . . . . . . . . . . 3
2.1.2 Graphene 的電子能帶結構 . . . . . . . . . . . . . . . . . . . . 4
2.1.3 Graphene 的應用 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 鐵磁性 (Ferromagnetism) . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 超順磁性 (superparamagnetic) . . . . . . . . . . . . . . . . . . . . . 7
3 實驗儀器、原理與過程 9
3.1 低能量電子繞射儀 (LEED) . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.1 原理 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.2 裝置 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2 光電子發射顯微鏡 (PEEM) . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3 X 射線磁圓偏振二向性 (X-ray magnetic circular dichroism；XMCD) 16
3.4 掃描試穿隧電子顯微鏡 (STM) . . . . . . . . . . . . . . . . . . . . . . 18
3.4.1 電子穿隧效應 . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.4.2 成像模式 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.4.3 Scanning tunneling spectroscopy (STS) . . . . . . . . . . . . 21
3.4.4 製備 graphene 的過程 . . . . . . . . . . . . . . . . . . . . . . 21
4 實驗結果與討論 23
4.1 Graphene 的製備 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.1.1 析出 (segregate) . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.1.2 LEED 與 graphene 原子解析圖的對照 . . . . . . . . . . . . . 24
4.1.3 藉由 LEED 判斷 graphene 的特性 . . . . . . . . . . . . . . . 25
4.1.4 藉由 STM 判斷 graphene 的特性 . . . . . . . . . . . . . . . . 30
4.2 討論 Co/graphene 的磁性與結構 . . . . . . . . . . . . . . . . . . . . 38
4.2.1 透過 LEED 圖案確認 grpahene 的成長 . . . . . . . . . . . . . 38
4.2.2 不同厚度下的磁性結果 . . . . . . . . . . . . . . . . . . . . . . 38
4.2.3 磁性與成長模式的關係 . . . . . . . . . . . . . . . . . . . . . . 44
5 結論 51

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