Sub-micron phase coexistence in small-molecule organic thin films revealed by infrared nano-imaging.
Sub-micron phase coexistence in small-molecule organic thin films revealed by infrared nano-imaging.
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DOI：
10.1038/ncomms5101
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发表时间：
2014-06-11
影响因子：
16.6
通讯作者：
Nickel, Bert
中科院分区：
文献类型：
--
作者：
Westermeier, Christian;Cernescu, Adrian;Amarie, Sergiu;Liewald, Clemens;Keilmann, Fritz;Nickel, Bert
控制有机薄膜中的畴尺寸和结晶度对于诸如有机光致发光的电子应用是非常重要的，但是合适的纳米尺度映射是非常困难的。在这里，我们应用红外光谱纳米成像直接确定20纳米分辨率的有机薄膜的局部结晶度。我们发现，国家的最先进的并五苯薄膜（生长在SiO2在升高的温度下）是结构上不均匀的，但在亚微米尺度上表现出两个相互渗透的阶段，记录的位移振动共振。我们观察到体相成核的主导并五苯薄膜相内的独特的椭圆形，并在存储过程中进一步增长。微弱的地形对比以及X射线分析证实了我们的解释。由于体相成核阻碍了薄膜相内的载流子渗透路径，因此迄今为止不受控制的结构不均匀性可能会引起关于并五苯载流子迁移率的相互矛盾的报道。纳米级多晶现象的光谱纳米成像将具有从有机纳米复合物到地质矿物的许多应用。 在有机半导体并五苯薄膜器件中，两种共存相之间的晶界会阻碍电荷的传输。Westermeier等人使用红外光谱纳米成像来显示联锁形态，这与其晶粒结构无关。
Controlling the domain size and degree of crystallization in organic films is highly important for electronic applications such as organic photovoltaics, but suitable nanoscale mapping is very difficult. Here we apply infrared-spectroscopic nano-imaging to directly determine the local crystallinity of organic thin films with 20-nm resolution. We find that state-of-the-art pentacene films (grown on SiO2 at elevated temperature) are structurally not homogeneous but exhibit two interpenetrating phases at sub-micrometre scale, documented by a shifted vibrational resonance. We observe bulk-phase nucleation of distinct ellipsoidal shape within the dominant pentacene thin-film phase and also further growth during storage. A faint topographical contrast as well as X-ray analysis corroborates our interpretation. As bulk-phase nucleation obstructs carrier percolation paths within the thin-film phase, hitherto uncontrolled structural inhomogeneity might have caused conflicting reports about pentacene carrier mobility. Infrared-spectroscopic nano-imaging of nanoscale polymorphism should have many applications ranging from organic nanocomposites to geologic minerals. The grain boundaries between two coexisting phases in organic semiconductor pentacene are expected to obstruct charge transport in its thin-film devices. Westermeier et al. use infrared-spectroscopic nano-imaging to show an interlocking morphology, which is uncorrelated with its grain structures.
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影响因子：
3.2
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