Exploring the F16CoPc/Ag(110) Interface Using Scanning Tunneling Microscopy and Spectroscopy. 2. Adsorption-Induced Charge Transfer Effect
Exploring the F16CoPc/Ag(110) Interface Using Scanning Tunneling Microscopy and Spectroscopy. 2. Adsorption-Induced Charge Transfer Effect
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DOI：
10.1021/jp1078295
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发表时间：
2010-12-16
影响因子：
3.7
通讯作者：
Hietschold, Michael
中科院分区：
文献类型：
--
作者：
Toader, Marius;Gopakumar, Thiruvancheril G.;Hietschold, Michael
先前研究的第二部分（Toader, M. J. Phys. Chem. C 2010, 114 (8), 3537-3543）在这项工作中提出，其中通过扫描隧道显微镜研究了超薄层钴（11）十六氟酞菁（F16CoPc）和贵金属Ag（110）单晶之间界面的电子特性（STM）和光谱（STS）。隧道电压极性相关的 STM 图像反映了由 Co (1,2 轨道与金属表面态重叠而产生的钴离子介导的隧道过程。电压极性依赖性基于界面处的电荷转移进行讨论，通过归一化微分电导率 (NDC) 光谱中可检测到的吸附诱导间隙态很好地维持。密度泛函理论 (DFT) 计算适用于整个对称取代钴酞菁 (Co Pc, F4CoPc、F8CoPc 和 F16CoPc），以阐明氟原子对能级以及最高占据分子轨道最低未占据分子轨道 (HOMO-LUMO) 能隙演化的影响。有机/金属界面处的能级排列，负责观察到的 LUMO 简并提升及其能量向费米能级的转移。
The second part of the previous study (Toader, M. J. Phys. Chem. C 2010, 114 (8), 3537-3543) is presented in this work where the electronic properties at the interface between an ultrathin layer of cobalt(11) hexadecafluoro-phthalocyanine (F16CoPc) and a noble metal Ag (110) single crystal, are investigated by means of scanning tunneling microscopy (STM) and spectroscopy (STS). The tunneling voltage polarity dependent STM image reflects a tunneling process mediated by the cobalt ion resulting from the overlapping of the Co (1,2 orbital with the metal surface states. The voltage polarity dependence is discussed based on a charge transfer at the interface, well sustained by the adsorption-induced gap states detectable in the normalized differential conductivity (NDC) spectra. Density functional theory (DFT) calculations are employed for the entire family of symmetrically substituted cobalt phthalocyanines (Co Pc, F4CoPc, F8CoPc, and F16CoPc) in order to elucidate the influence of the fluorine atoms on the energy levels as.well as on the highest occupied molecular orbital lowest unoccupied molecular orbital (HOMO-LUMO) gap evolution. Tip sample distance-dependent NDC spectra denote a pinning of the energy levels as a result of the strong molecule substrate interaction. The experimentally estimated level positions and gap value are compared with the DFT calculated ones in order to determine the energy level alignment at the organic/metal interface, responsible for the observed degeneracy lifting of the LUMO as well as its energy shift toward the Fermi level.