Characterization of Grain Structure in Block Copolymer Thin Films by Guided-wave Depolarized Light Scattering

该提案描述了导波去偏振光散射的发展，这是一种表征有序嵌段共聚物薄膜结构的新技术。该技术将使这些二维系统中有序形成和缺陷密度的成本效益、非破坏性、实时量化成为可能。通过将聚合物薄膜沉积在低折射率衬底（熔融二氧化硅）上，可以制造平面光波导。标准的光波导元件，如棱镜耦合器，将用于耦合进入薄膜的激光束和从薄膜中散射出来的光。去偏振散射光束将被引导穿过薄膜，并使用CCD相机进行检测。相当大的努力将致力于开发易于处理的模型，将检测到的光信号与薄膜内的颗粒结构联系起来。为大块嵌段共聚物样品的光学性质建立的模型将作为这一发展的起点。初步预测表明，导波的几何形状将导致被探测信号性质的根本差异。用导波去偏振光散射法测定了相同样品在互易空间中的晶粒结构，并与用扫描电子显微镜（SEM）和原子力显微镜（AFM）实验得到的位置空间数据进行了比较。提出的工作建立在早期的工作，由共同的pi在三维嵌段共聚物样品的晶粒结构的光学表征。这一信息对于嵌段共聚物薄膜的一些最近提出的应用至关重要，如信息存储和光子学。提出的研究也将回答关于衬底和界面对薄嵌段共聚物薄膜中有序形成和缺陷湮灭的影响的基本问题。

The proposal describes the development of guided-wave depolarized light scattering, a novel technique for characterizing the structure of ordered block copolymer thin films. This technique will enable cost-effective, nondestructive, real-time quantification of order formation and defect density in these two-dimensional systems. A planar optical waveguide will be fabricated by depositing the polymer film on a low refractive index substrate (fused silica). Standard optical waveguide elements such as prism couplers will be used to couple the laser beam into the film and the scattered light out of the film. The depolarized scattered beam will be guided through the film and detected using a CCD camera. Considerable effort will be devoted to the development of tractable models for relating the detected optical signal to the grain structure within the film. The models that have been established for the optical properties of bulk block copolymer samples will serve as a starting point for this development. Preliminary predictions indicate that the guided-wave geometry will lead to fundamental differences in the nature of the detected signal. The grain structure determined in reciprocal space by the guided-wave depolarized light scattering studies will compared with position space data obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM) experiments on the same samples.The proposed work builds on earlier work by the co-PIs on optical characterization of grain structure in three-dimensional block copolymer samples. This information is crucial for a number of recently proposed applications for block copolymer thin films such as information storage and photonics. The proposed research will also answer fundamental questions regarding the influence of substrates and interfaces on order formation and defect annihilation in thin block copolymer films.