Chain-length dependent growth dynamics of n-alkanes on silica investigated by energy-dispersive x-ray reflectivity in situ and in real-time.
Chain-length dependent growth dynamics of n-alkanes on silica investigated by energy-dispersive x-ray reflectivity in situ and in real-time.
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DOI：
10.1063/1.4719530
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发表时间：
2012-05
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影响因子：
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通讯作者：
C. Weber;C. Frank;S. Bommel;T. Rukat;W. Leitenberger;P. Schäfer;F. Schreiber;S. Kowarik
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文献类型：
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作者：
C. Weber;C. Frank;S. Bommel;T. Rukat;W. Leitenberger;P. Schäfer;F. Schreiber;S. Kowarik
我们比较了三种正构烷烃C（36）H（74），C（40）H（82）和C（44）H（90）在SiO（2）上的生长动力学，使用实时和原位能量色散X射线反射率。所有的分子研究对齐在基板上的直立的方向，并表现出从逐层生长的过渡到岛生长后，约4单层的条件下采用。在倒易空间中的五个不同点的反射强度的同时拟合表明，较长的正构烷烃形成的膜在生长过程中更快地粗糙化。这种行为可以解释为一个链长依赖的高度的Ehrlich-Schwoebel势垒。生长后的进一步X射线衍射测量表明，由较长的正构烷烃组成的膜在顶部区域中也包含更多的平躺分子。虽然结果揭示了链状分子的典型行为，但这些发现也可用于优化有机场效应晶体管，其中需要光滑的正构烷烃夹层，而不需要两个或更多个分子取向的共存。
We compare the growth dynamics of the three n-alkanes C(36)H(74), C(40)H(82), and C(44)H(90) on SiO(2) using real-time and in situ energy-dispersive x-ray reflectivity. All molecules investigated align in an upright-standing orientation on the substrate and exhibit a transition from layer-by-layer growth to island growth after about 4 monolayers under the conditions employed. Simultaneous fits of the reflected intensity at five distinct points in reciprocal space show that films formed by longer n-alkanes roughen faster during growth. This behavior can be explained by a chain-length dependent height of the Ehrlich-Schwoebel barrier. Further x-ray diffraction measurements after growth indicate that films consisting of longer n-alkanes also incorporate more lying-down molecules in the top region. While the results reveal behavior typical for chain-like molecules, the findings can also be useful for the optimization of organic field effect transistors where smooth interlayers of n-alkanes without coexistence of two or more molecular orientations are required.