Dewetting-Induced Hierarchical Patterns in Block Copolymer Films

Thin film stability should be carefully monitored in many practical applications and at the same time can be effectively utilized to produce the surface pattern. In this work, it is demonstrated that block copolymer thin films can generate highly ordered, hierarchical surface pattern via combined process of self-assembly and film destabilization. The dewetting process generates the surface pattern of hole or island on the micrometer scale while the self-assembly produces well-ordered pattern on the nanometer scale. Highly ordered nanostructure is obtained by solvent annealing within the remaining part of dewetted film, and its orientation is systematically controlled by adjusting the relative humidity, ultimately leading to fine-tuned hierarchical surface pattern with high degree of lateral order. As a simple example, the formation of hierarchical structure containing Au nanowire along the block copolymer domains on the dewetted films illustrates that our simple approach can offer great opportunity to generate true hierarchical, complex patterns.