我們以角解析光電子能譜研究CuPc在銀薄膜/鍺(111)和CuPc在銀薄膜/金(111)的界面電子結構。要得到良好平整的銀薄膜，我們在130 K蒸鍍銀之後馬上退火到室溫。當製備好平整的銀薄，我們之後便在室溫鍍上CuPc和測量光電子能譜。雖然CuPc都蒸鍍在銀薄膜上，當基底不同時，CuPc和銀薄膜的介面電子結構也會有所改變。當CuPc鍍在銀薄膜/金(111)時，其電子結構和CuPc鍍在銀(111)基板上相似。而當CuPc鍍在銀薄膜/鍺(111)時，我們觀察到了間隙態(gap state)，它產生在銀量子井態和鍺重洞能帶交互作用的間隙，所以間隙態的能量位置會因銀薄膜厚度而改變。而CuPc最高電子佔據軌域會因為間隙態去對齊費米面的緣故而使得能量位置跟著改變。由此可知，雖然CuPc都鍍在銀薄膜上，CuPc和銀薄膜的界面電子結構會受到銀薄膜下基板的影響而有所不同。

We have studied interfacial behavior of CuPc on Ag thin films/Ge(111) and Ag thin films/Au(111) by angle-resolved photoemission spectroscopy (APRES). To preparing a well-ordered Ag thin film, we deposited Ag at about 130 K and then annealed it to room temperature. After obtaining a uniform Ag thin film, we started to evaporate CuPc on Ag film and perform APRES measurement at room temperature. Although CuPc is all deposited on the Ag thin films, the interfacial electronic structure between CuPc and Ag film changes when substrate is different. For CuPc on Ag thin film/Au(111), the electronic structure of CuPc is similar to CuPc on Ag(111), while for CuPc/Ag films/Ge(111), gap state appears at the band edge of the gap which is caused by the interaction between Ag QWS and Ge heavy hole band edge, so the gap state position will change with the thickness of Ag thin film. With the presence of gap state to pin the Fermi level, the HOMO position of CuPc changes with the thickness of Ag thin film. From these evidences, we can conclude that, although CuPc is deposited on the same Ag thin film, the interfacial electronic structures between CuPc and Ag can be different due to the influence from the substrate below the Ag thin film.

[1]H. Ishii, K. Sugiyama, E. Ito, and K. Seki, Adv. Mater. 11, 605 (1999)
[2]Stefan H¨ufner, Photoelectron Spectroscopy, Springer
[3]Dominic A. Ricci, Photoemission Studies of Interface Effects on Thin Film
Properties, Ph.D. thesism, University of Illinois at Urbana-Champaign (2006)
[4]User Manual SCIENTA R3000, VG SCIENTA
[5]http://www.nsrrc.org.tw
[6]S.T. Lee, Y. M. Wang, and X.Y. Hou, Appl. Phys. Lett. 74, 670 (1990)
[7]Ingo Kröger et al 2010 New J. Phys. 12 083038
[8]A.Scheybal et al Phys. Rev. B 79 (2009) 115406
[9]F.Forster et al 2006 Surface Science 600 3870-3874
[10]C. Huckstadt et al Phys. Rev. B 73 (2006) 075409
[11]C.G. Sanchez et al Langmuir 18 (2002) 6628.
[12]H.Y. Mao et al Organic Electronics 12 (2011) 534-540
[13]D.-A. Luh* , C.-M. Cheng, K.-D. Tsuei, and J.-M. Tang, Phys. Rev. B 78, 233406 (2008)
[14]S.-J. Tang, W.-K. Chang, Y.-M. Chiu, H.-Y Chen, C.-M. Cheng, and K,-D.
Tsuei, Phys. Rev. B 78, 245407 (2008)
[15]Che-Chia Hsu, 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, Master thesism, National Tsing Hua University(2010)
[16] Noboru Takeuchi, et al Phys Rev. B 43 17 (1991)
[17] A. Beckmann, et al. Phys Rev. B, 48 3 (1993)