Optical and electronic interaction at metal-organic and organic-organic interfaces of ultra-thin layers of PTCDA and SnPc on noble metal surfaces
详细信息 查看全文
- 作者：Marco Gruenewald ; Kristin Wachter ; Matthias Meissner ; Michael Kozlik ; Roman Forker ; Torsten Fritz
- 关键词：Optical Differential Reflectance Spectroscopy (DRS) ; Organic molecular beam epitaxy (OMBE) ; Thin films ; Ag(1 ; 1 ; 1) ; Au(1 ; 1 ; 1)
- 刊名：Organic Electronics
- 出版年：2013
- 出版时间：September, 2013
- 年：2013
- 卷：14
- 期：9
- 页码：2177-2183
- 全文大小：1069 K
文摘
We investigate the interaction mechanisms at metal-organic and organic-organic interfaces in highly-ordered ultra-thin layers of the dye molecules 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) and tin(II)-phthalocyanine (SnPc) on single crystalline noble metals. The ultra-thin films are characterized by means of in situ differential reflectance spectroscopy (DRS), followed by an extraction of the optical functions by application of a numerical algorithm. For the first time, DRS data of PTCDA and SnPc films on Ag(1 1 1) are presented. We found that for the contact layers of PTCDA and SnPc the well-known covalent interaction between adsorbate and substrate is manifested in broad and structureless absorption spectra. Surprisingly, the optical spectra of the respective first monolayers on Ag(1 1 1) are almost identical despite of the rather different electronic structure of the free molecules. The special character of the optical spectra is emphasized by a comparison with PTCDA and SnPc monolayers on Au(1 1 1) where the electronic interaction at the metal-organic interface is much weaker. Quite differently from the contact layer, the second layer of the same molecule on Ag(1 1 1) clearly shows monomeric behavior which can only be observed if the electronic and optical coupling with the surrounding molecules and the substrate is faint. However, a very weak out-of-plane electronic interaction remains as concluded from the comparison with the spectra obtained on inert mica substrates. We also present structural data acquired with low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) of SnPc on Au(1 1 1).