A novel structural analysis for a cylinder-forming block copolymer thin film using neutron reflectivity aided by transmission electron microtomography
A novel structural analysis for a cylinder-forming block copolymer thin film using neutron reflectivity aided by transmission electron microtomography
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DOI：
10.1021/ma071334c
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发表时间：
2007-09-18
期刊：
影响因子：
5.5
通讯作者：
Jinnai, Hiroshi
中科院分区：
文献类型：
--
作者：
Niihara, Ken-ichi;Matsuwaki, Ukyo;Jinnai, Hiroshi
用中子反射法（NR）和透射电镜（TEMT）研究了氘代苯乙烯-嵌段-2-乙烯基吡啶（dPS-b-P2 VP）嵌段共聚物薄膜的微相分离结构。dPS-b-P2 VP嵌段共聚物在本体状态下显示出圆柱形形态。将嵌段共聚物旋涂在Si基底上，在NR实验之前将其广泛退火（170 ℃持续14天）。退火后的薄膜呈现出无特征的NR轮廓，反射率沿薄膜深度方向沿着随散射矢量qz的增大而单调减小。通过TEMT检查NR实验中使用的dPS-b-P2 VP嵌段共聚物薄膜的部分，由此成功地获得嵌段共聚物薄膜的三维（3D）形态。3D图像清楚地表明，薄膜内部的微相分离结构具有圆柱形形态，沿深度沿着具有一定的顺序，但几乎没有面内顺序。为了通过传统的模型拟合方法分析NR分布，需要呈现浓度分布的模型结构作为初始“猜测”。在这项研究中，两个不同的模型，即，(i)六角填充P2 VP圆柱体铺设平行于Si衬底的基础上已知的晶格参数，和（ii）实验获得的TEMT三维结构，提出了建议。从这两个模型中评价的浓度曲线用作计算曲线与实验获得的NR曲线R-exp拟合的初始猜测。结果发现，基于前一个模型的拟合失败，而基于后一个模型的拟合有一个很好的拟合Rexp，这一结果表明，微相分离结构，不是完美的周期性或取向仍然可以分析我们的新技术。
Microphase-separated structures of a poly(deuterated styrene-block-2-vinylpyridine) (dPS-b-P2VP) block copolymer in thin films were studied by neutron reflectivity (NR) and transmission electron microtomography (TEMT). The dPS-b-P2VP block copolymer shows a cylindrical morphology in the bulk state. The block copolymer was spun-coated on a Si substrate, which was extensively annealed (170 degrees C for 14 days) before the NR experiments. The annealed thin film showed a featureless NR profile, the reflectivity monotonically decreased with the increasing scattering vector along the depth direction of the thin film, qz. The portion of the dPS-b-P2VP block copolymer thin film used in the NR experiment was examined by TEMT, from which a three-dimensional (3D) morphology of the block copolymer thin film was successfully obtained. The 3D image clearly showed that the microphase-separated structure inside the thin film had a cylindrical morphology with some order along the depth, but almost no in-plane order. In order to analyze the NR profile by a conventional model fitting method, a model structure that exhibits a concentration profile is necessary as an initial "guess". In this study, two different models, i.e., (i) hexagonally packed P2VP cylinders laying parallel to the Si substrate based on the known lattice parameters, and (ii) experimentally obtained TEMT 3D structure, were proposed. The concentration profiles evaluated from these two models were used as the initial guesses in the fitting of the calculated profiles to the experimentally obtained NR profile, R-exp. It was found that the fitting based on the former model failed, while the fitting based on the latter one had an excellent fit to the Rexp, This result demonstrates that the microphase-separated structures that are NOT perfectly periodic nor oriented can still be analyzed by our new technique.