Wu Xiang-Fa, Dzenis Yuris A
Department of Engineering Mechanics, Center for Materials Research and Analysis, University of Nebraska-Lincoln, Lincoln, NE 68588-0526, USA.
J Chem Phys. 2006 Nov 7;125(17):174707. doi: 10.1063/1.2363982.
We study the guided self-assembly of symmetric/asymmetric diblock copolymer (BCP) films on heterogeneous substrates with chemically patterned surface by using a coarse-grained phase-separation model. During the procedure, the free energy employed for the BCP films was modeled by the Ginzburg-Landau free energy with nonlocal interaction, and the flat, chemically patterned surface was considered as a heterogeneous surface with short-range interaction with the BCP molecules. The resulting Cahn-Hilliard equation was solved by means of an efficient semi-implicit Fourier-spectral algorithm. Effects of pattern scale, surface chemical potential, and BCP asymmetry on the self-assembly process were explored in detail and compared with those without chemically patterned substrate surfaces. It was found that the morphology of both symmetric and asymmetric BCP films is strongly influenced by the commensurability between the unconstrained natural period lambda* of the bulk BCP and the artificial pattern period. Simulation shows that patterned surface with period close to lambda* leads to highly ordered morphology after self-assembly for both symmetric and asymmetric BCP films, and it also dramatically accelerates the guided self-assembly process. The present simulation is in a very good agreement with the recent experimental observation in BCP nanolithography. Finally, the present study also expects an innovative nanomanufacturing method to produce highly ordered nanodots based on the guided self-assembly of asymmetric BCP films on chemically patterned substrates.
我们使用粗粒化相分离模型，研究了对称/不对称双嵌段共聚物（BCP）薄膜在具有化学图案化表面的异质衬底上的导向自组装过程。在此过程中，BCP薄膜的自由能通过具有非局部相互作用的金兹堡-朗道自由能进行建模，平坦的化学图案化表面被视为与BCP分子具有短程相互作用的异质表面。通过高效的半隐式傅里叶谱算法求解由此得到的Cahn-Hilliard方程。详细探讨了图案尺度、表面化学势和BCP不对称性对自组装过程的影响，并与没有化学图案化衬底表面的情况进行了比较。结果发现，对称和不对称BCP薄膜的形态都受到本体BCP的无约束自然周期λ与人工图案周期之间的可公度性的强烈影响。模拟表明，对于对称和不对称BCP薄膜，周期接近λ的图案化表面在自组装后会导致高度有序的形态，并且还显著加速了导向自组装过程。目前的模拟与BCP纳米光刻中最近的实验观察结果非常吻合。最后，本研究还期望基于不对称BCP薄膜在化学图案化衬底上的导向自组装，开发一种创新的纳米制造方法来生产高度有序的纳米点。
