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Self-assembly of α-6T Molecule on Ag(100) and Related STM Induced Luminescence
Liu-guo Chen,Chao Zhang,Rui Zhang,Zhen-chao Dong*
Author NameAffiliationE-mail
Liu-guo Chen Hefei National laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China  
Chao Zhang Hefei National laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China  
Rui Zhang Hefei National laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China  
Zhen-chao Dong* Hefei National laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China zcdong@ustc.edu.cn 
Abstract:
We have investigated the self-assembly and light emission properties of organic α-sexithiophene (α-6T) molecules on Ag(100) under different coverage by scanning tunneling microscopy (STM). At very low coverage, the α-6T molecules form a unique enantiomer by grouping four molecules into a windmill supermolecular structure. As the coverage is increased, α-6T molecules tend to pack side by side into a denser stripe structure. Fur-ther increase of the coverage will lead to the layer-by-layer growth of molecules on Ag(100) with the lower-layer stripe pattern serving as a template. Molecular fluorescence for α-6T molecules on Ag(100) at a coverage of five monolayers has been detected by light excitations,which indicates a well decoupled electronic states for the top-layer α-6T molecules. How-ever, the STM induced luminescent spectra for the same sample reveal only plasmonic-like emission. The absence of intramolecular fluorescence in this case suggests that the elec-tronic decoupling is not a sufficient condition for generating photon emission from molecules. For intramolecular fluorescence to occur, the orientation of the dynamic dipole moment of molecules and the energy-level alignment at the molecule-metal interface are also important so that molecules can be effectively excited through efficient dipolar coupling with local plasmons and by injecting holes into the molecules.
Key words:  α-Sexithiophene, Self-assembly, Scanning tunneling microscopy, Tunneling electron induced luminescence, Surface plasmon, Plasmon-exciton coupling
FundProject:
Ag(100)表面α-6T分子的自组装和STM诱导发光
陈留国,张超,张瑞,董振超*
摘要:
利用扫描隧道显微镜诱导发光技术, 对有机分子α-6T在Ag(100)表面的自组装和光子发射特性进行了研究. 发现在极低的覆盖率下,α-6T分子以四个分子形成一种独特的风车形状的异构体. 随着覆盖率的增加,α-6T分子倾向于肩并肩紧密排列形成条纹状结构. 进一步增加覆盖率时,分子以低层分子的条纹结构作为模板,一层一层往上生长. 在五层分子厚度的样品上,利用光致方法可以获得分子荧光,这说明顶层分子已经被有效脱耦合. 然而在同样的样品上,STM诱导发光光谱却只展现出类似等离激元的发射特性. 在这种情况下,分子荧
关键词:  α-6T,自组装,扫描隧道显微技术,隧穿电子诱导发光,表面等离激元,等离激元-激子耦合
DOI:10.1088/1674-0068/24/06/659-664
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