Chemical Fingerprints of Large Organic Molecules in Scanning Tunneling Microscopy: Imaging Adsorbate-Substrate Coupling of Metalloporphyrins
Chemical Fingerprints of Large Organic Molecules in Scanning Tunneling Microscopy: Imaging Adsorbate-Substrate Coupling of Metalloporphyrins
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DOI：
10.1021/jp904680c
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发表时间：
2009-09-17
影响因子：
3.7
通讯作者：
Marbach, Hubertus
中科院分区：
文献类型：
--
作者：
Buchner, Florian;Warnick, Karl-Georg;Marbach, Hubertus
在这种结合的实验和理论工作中，我们证明了在Ag（111）上的四苯基卟啉的例子中，如何利用单个吸附物轨道的差异及其与衬底的相互作用来切换扫描隧道显微镜（STM）实验中吸附物的外观，使得电子和化学上非常相似的大分子在STM中变得可区分。特别地，研究了在Ag（111）上由2HTPP（TPP =四苯基卟啉）、CoTPP和FeTPP分子组成的混合层，并且证明了在不同偏压下获得的STM图像构成了混合层内不同分子的指纹。通过密度泛函计算，可以详细解释所观察到的特征，并追溯到吸附分子与表面的直接轨道相互作用。因此，在计算中对表面的明确考虑对于与实验取得良好的一致性是决定性的。
In this combined experimental and theoretical work we demonstrate at the example of tetraphenylporphyrins on Ag(111) how differences in individual adsorbate orbitals and their interaction with the substrate can be exploited to switch the appearance of the adsorbate in scanning tunneling microscopy (STM) experiments, such that electronically and chemically very similar large molecules become distinguishable in STM. in particular, an intermixed layer consisting of 2HTPP (TPP = tetraphenylporphyrin), CoTPP, and FeTPP molecules on Ag(111) was investigated, and it is demonstrated that STM images acquired with different bias voltages constitute fingerprints of the different molecules within the intermixed layer. By means of density functional calculations the observed features could be explained in detail and traced back to a direct orbital interaction of the adsorbed molecule with the surface. The explicit consideration of the surface in the calculations therefore turned out to be decisive to achieve good agreement with experiment.