調控有機分子在金屬表面的電子結構及傳輸行為

Controlling Electronic Structures and Transport Properties of Organic Molecules on Metallic Surfaces

徐創涵(Chuang-Han Hsu)

指導教授 ： 林敏聰

共同指導教授 ： 關肇正(Chao-Cheng Kaun)

國立臺灣大學/理學院/物理研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.10728

摘要

藉由分子的高可撓性和複雜製成的高完成性，設計以分子為基底的裝置引起廣泛的關注。其中，有機材料和金屬結合的分子因具有特殊的磁性行為，因此此類分子有相當大的潛力來達成奈米尺度的自旋電子元件。但因為在設計過程中，分子經常須被放置在基底上，如果要完成功能性的自旋電子元件，分子和外界的交互作用須要被清楚的了解。因此在一開始，我們藉由掃描穿隧電子顯微鏡結合第一原理計算來研究錳酞花青分子在銅(111)和鈷在銅(111)上的吸附行為，在研穿過程中我們發現，凡得瓦力的加入，在銅(111)的計算上可以得到可跟實驗比較的結果。藉由改變分子和基底及分子跟分子之間的作用力，我們發現這些作用力會帶給分子相當大的影響。
此外，利用自旋極化掃描穿隧電子顯微鏡，錳酞花青分子在鈷/銅(111)的磁性行為可被探討。為更清楚探討此處的磁性行為，我們計算了以自旋極化掃描穿隧電子顯微鏡量測樣品的結構為模型的自旋傳輸特性，藉此希望能更合理的來解釋實驗結果。更進一歩，藉由改變磁性針和樣品的距離，上述的傳輸行為可以被調控，我們認為是存在於錳酞花青分子和鈷/銅(111)間的兩者主要作用力造成此影響，這兩個作用分為是s和p電子軌域的混成和齊納磁耦合作用力。

關鍵字

第一原理計算 ； 非平衡格林函數 ； 錳酞花青 ； 自旋極化穿隧電子顯鏡 ； 自旋傳輸

並列摘要

Design of the molecule-based system has attracted interest due to its broad
flexibility for realizing highly complex processes. Especially, the organic-metallics
molecules provide unique magnetic characteristics which give a possibility to realize
nanoscale spintronic devices. However, molecules play a part in the environment of a
device since they are frequently placed on substrates. Thus, in order to design a real
functionality in spintronic devices, the fundamental study of the basic interactions
of the molecules with the environment is an essential work. At first, we study the
adsorption behaviors of ManganesePhthalocyanine (MnPc) molecules on Cu(111)
and Co/Cu(111) surfaces by a combined investigation of STM measurements and
ab initio calculations. In this part, the Van der Waals forces are involved to give a
reliable atomic configuration compared to STM images of MnPc/Cu(111). From the
results, the various molecule-substrate and molecule-molecule interactions reveal a
significant influence on electronic and magnetic properties of MnPc molecules.
In addition, SP-STS measurements are performed to investigate the magnetic
coupling at the interface between the MnPc molecule and Co/Cu(111) surface. A
spin transport model based on the NEGF-DFT framework, using STM-moleculesubstrate
as a nanojunction, has provided a better understanding on SP-STS results.
More importantly, this spin transport model indicates a controllable spin transport
behavior of the nanojunction via various tip-sample separations, which is due to the
subtle balance of the sp hybridization and the Zener exchange coupling between the
tip and MnPc.

並列關鍵字

Ab initio calculation ； ManganesePhthalocyanine ； SP-STM ； spin transport

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