掃描穿隧顯微術研究Cu(111)單晶表面之鐵-苝四甲酸二酐(Fe-PTCDA)的排列與電子結構

Monolayer Structure and Electronic Properties of Fe-Perylenetetracarboxylic-dianhydride (Fe-PTCDA) on Cu(111)

蔡旭涵(Hsu-Han Tsai)

指導教授 ： 陳俊顯

國立臺灣大學/理學院/化學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.02936

摘要

本論文研究 Cu(111)單晶表面的苝四甲酸二酐(PTCDA)與鐵-苝四甲酸二酐
(Fe-PTCDA)兩種單層分子膜的排列與電子結構。Fe-PTCDA 錯合物的排列結構由
掃描穿隧顯微術(STM)加以分析；PTCDA 和Fe-PTCDA 的電子結構以掃描穿隧能
譜(STS)進行量測。
在研究初期，儀器並未順利運作，無法在標準試片(HOPG)表面上得到原子級
解析度，也未能進行掃描穿隧能譜實驗。藉由最佳化濺射探針的參數以改善探針的
品質、改善腔體的真空度、改善儀器接地和微調防震桌水平度等方式，方得以經常
地獲得HOPG 原子級解析度之影像，並以此為標準校正STM 的壓電驅動器。在安
裝並設定鎖相放大器之後，先後以HOPG、Cu(111)和Ag(111)表面測試，可成功地
獲得dI/dV 能譜和駐波的dI/dV 圖。
實驗方法為先準備Cu(111)單晶表面；經由熱阻式蒸鍍獲得PTCDA/Cu(111)樣
品；或是同時蒸鍍鐵和PTCDA 分子，再經最後加熱而得Fe-PTCDA/Cu(111)樣品。
dI/dV 能譜顯示PTCDA 的最低未占軌域(LUMO)與Cu(111)形成混成態，STM 影像
亦確認此結果。STM 影像顯示Fe-PTCDA 在Cu(111)表面係由兩種位向分子(鏈型
和桄型)構成梯狀排列，且兩種分子的占有態能階相同；從dI/dV 能譜進一步獲知
此占有態能階是由Fe-PTCDA 的LUMO 與Cu(111)所形成之混成態。dI/dV 能譜同
時顯示桄型分子在未占有態具有較鏈型分子高的能態密度，代表鏈型PTCDA 的
LUMO 被鐵原子提供的電子完全占有而桄型PTCDA 的LUMO 僅被部分占有。由
於鏈型分子與4 個鐵原子配位，而桄型分子僅配位2 個鐵原子，可知鐵與PTCDA
間的電荷轉移與配位數有關。

關鍵字

掃描穿隧顯微術 ； 掃描穿隧能譜 ； Cu(111) ； 苝四甲酸二酐 ； 金屬-有機錯合物 ； 電荷轉移

並列摘要

This thesis presents the investigation of PTCDA (3,4,9,10-perylenetetracarboxylicdianhydride)
and Fe-PTCDA complex on Cu(111). Monolayer structure of Fe-PTCDA
was studied by scanning tunneling microscopy (STM); electronic properties of PTCDA
and Fe-PTCDA were measured by scanning tunneling spectroscopy (STS). dI/dV
spectra of PTCDA on Cu(111) revealed the formation of a hybrid state, indicative of a
strong chemical interaction between the adsorbate and substrate. The molecular orbital
involved in the hybridization was LUMO (lowest unoccupied molecular orbital),
confirmed by topographic images. Topographic images of Fe-PTCDA/Cu(111)
revealed a ladder-like structure, which is distinctly different from the herringbone
structure of PTCDA/Cu(111). Two types of molecules were named according to their
orientation in a ladder-like structure, that is, chain- and rung-PTCDA. Topographic
features of chain- and rung-PTCDA resolved at the molecular level are unprecedented.
The images unraveled that both types of molecules had the same occupied molecular state.
However, dI/dV spectra showed that rung-PTCDA have higher density of unoccupied
states compared with chain-PTCDA. This means that the LUMO of rung-PTCDA is
only partially occupied with the electrons donated by Fe. Since chain-PTCDA binds to
4 Fe atoms while rung-PTCDA binds to only 2 Fe atoms, the result showed that the charge
transfer from Fe to PTCDA is coordination number-related.

並列關鍵字

Scanning Tunneling Microscopy ； Scanning Tunneling Spectroscopy ； Cu(111) ； PTCDA ； Metal-organic Complex ； Charge Transfer

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