Self-assembled block copolymer templates for atomic layer deposition: The effect of processing solvent

Abstract

In this study thin films of a rod-coil block copolymer (BCP) are deposited from different solvents and used as templates for atomic layer deposition (ALD) of ZnO. The BCP, P3HT-b-PEO, is known to self-organize into fiber-like phase-separated nanostructures, with central crystalline P3HT domains and outer amorphous PEO domains. The P3HT block in this study is short so that the size of the P3HT domains in the films is solvent insensitive. However, processing from poor PEO solvents results in thin PEO domains and good PEO solvents allow extended PEO chains and wide domains. The crystallinity of the P3HT-block and the affinity of the PEO-block to the ALD ZnO precursors lead to selective deposition of ZnO in the PEO domains. Therefore, the solvent-controlled morphology of the PEO domains in the BCP films can be translated to the size, distribution and morphology of the deposited ZnO. We show that films with swollen PEO domains have higher ZnO uptake compared to films with collapsed PEO chains. Furthermore, oriented PEO domains template oriented ZnO domains and wormlike morphologies direct wormlike ZnO nanostructures. Therefore, solvent selection is a toll to manipulate the BCP self-assembly and hence the ALD template and the morphology of the hybrid organic/inorganic film.