Studies of the interfacial structure and behavior of QWS for a well-ordered ultrathin film of tetratetracontane (n-C44H90; TTC)/Ag thin film/Ge(111) by ARPES

角解析光電子能譜研究TTC 於銀薄膜在鍺(111)基底上之介面結構及量子井態之行為

許哲嘉(Che-Chia Hsu)

指導教授 ： 唐述中

國立清華大學/理學院/物理學系/碩士(2011年)

https://doi.org/10.6843/NTHU.2011.00033

摘要

我們利用角解析光電子能譜研究tetratetracontane (n-C44H90; TTC)在銀薄膜上量子井態的行為。我們發現在鍍上TTC之後，量子井態(Quantum-well state)會往費米能階平移，而此趨勢與真空態(Vacuum level)的平移趨勢相符合。量子井態些許地向費米能階平移代表費米面所包圍的面積縮小，亦即電子態密度減小。對於研究量子井態的行為更能夠合理地解釋電子在介面的行為，由於量子井態的波函數束縛在金屬薄膜內並不會受到有機薄膜的破壞，而所量測到的真空態平移為 -0.62 eV。我們提出一個模型來解釋此介面的機制，根據量子井態的變化以及真空態的平移，mirror force支配著介面的電荷分布，我們假設像電荷效應(Image charge effect) 發生在此介面。此外，我們也得到分子軌域的能帶色散(Energy band dispersion)，我們觀察到分子內(Intra-molecular)以及分子間(Inter-molecular)能帶色散，與之前Ishii團隊所量測以及計算的相符合。此外，額外的能帶色散我們推測是由於TTC分子由於鍺基底的三軸對稱(Three-fold symmetry)而作60度角的排列而得到。

關鍵字

角解析光電子能譜 ； 量子井態

並列摘要

We have investigated the quantum-well-state (QWS) behavior of Ag thin film with tetratetracontane (n-C44H90; TTC) deposited on top by angled-resolved photoemission spectroscopy (AR-PES). We found that QWS shift towards Fermi level and the trend is consistent with vacuum level (VL) shifts. The slight shift of QWS towards Fermi level means that the area of the Fermi surface enclosed by the QWS bands shrinks and consequently the occupied charge density should decrease. It is more reasonable to discuss the charge behaviors at the interface by the investigation of the behaviors of QWS. As the wave functions of QWS are confined within the metal film, they will not be destroyed after the deposition of organic thin films. We had measured the VL shift Δ, which is about - 0.62 eV. We bring up a model to explain the mechanism at the interface. According to the results of QWS change and VL shift, the mirror force seems to dominate the charge distribution and we can speculate that the image charge effect takes place at the interface. We also obtained the energy band dispersion of the occupied molecular orbital state. Both the inter-molecular and the intra-molecular band dispersions were observed, which are consistent with the previous calculated and measured results by Ishii et al. However, extra energy band dispersions were also observed possibly due to the TTC molecules aligning 60 degrees with the others as a result of three-fold symmetry of the Ge(111) symmetry.

並列關鍵字

ARPES ； QWS ； TTC

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