Molecular resolution in dynamic force microscopy:: topography and dissipation for weakly interacting systems
Molecular resolution in dynamic force microscopy:: topography and dissipation for weakly interacting systems
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DOI：
10.1088/0957-4484/18/8/084004
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发表时间：
2007-02-28
期刊：
影响因子：
3.5
通讯作者：
Moeller, R.
中科院分区：
文献类型：
--
作者：
Fendrich, M.;Kunstmann, T.;Moeller, R.
动态力显微镜可用于研究有机分子在绝缘衬底上的生长。有机分子3，4，9，10-二萘嵌苯四甲酸二酐（PTCDA）在KBr（001）上具有Volmer-Weber生长.虽然大面积未被覆盖，但即使在低覆盖率下，也可以看到一些不同高度的PTCDA微晶，从两个单层（ML）到20 - 30 ML。在微晶的最上层，可以分辨单个分子。这种分子对比不仅表现在形貌上，而且表现在耗散信号上。这里，信号强烈地依赖于频移，即，尖端和样品之间的最小距离。当频移较大时，分子间的耗散增强，当频移较小时，形貌峰与耗散通道峰之间出现约0.2nm的位移。我们提出了一个模型，考虑到PTCDA的晶体生长，两个信号之间的转变是两个最顶层的分子的影响。
Dynamic force microscopy can be used to study the growth of organic molecules on insulating substrates. The organic molecule 3,4,9,10- perylenetetracarboxylic- dianhydride ( PTCDA) exhibits Volmer - Weber growth on KBr( 001). While large areas are uncovered, some PTCDA crystallites of different heights, from two monolayers ( ML) up to 20 - 30 ML, can be seen, even at low coverages. On the topmost layer of the crystallites, single molecules can be resolved. Such a molecular contrast does not only show in topography but also in the dissipation signal. Here, the signal strongly depends on the frequency shift, i.e., the minimum distance between tip and sample. At large frequency shifts, the dissipation is enhanced between the molecules, if the frequency shift is lower, a shift of 0.2 nm between the peaks in topography and dissipation channel occurs. We propose a model that takes the crystalline growth of PTCDA into account, the shift between both signals being an effect of the two topmost layers of molecules.