Conversion from self-assembled block copolymer nanodomains to carbon nanostructures with well-defined morphology

Abstract

We developed a method to fabricate arrays of nanostructured carbon materials of high quality, via direct pyrolysis of poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) block copolymer (BCP) as thin films without small organic molecules incorporated as carbon resources. Prior to pyrolysis, the nanodomains were cross-linked with UV radiation under nitrogen (UVIN). As upon pyrolysis thermal energy imparts mobility to nanodomains to overcome the constraints imposed by cross-linked chains, the free surface is inevitably covered with the PS block that has a smaller surface energy; unless favorable interactions with the P2VP block exist at the free surface, the outer layer of carbonaceous films is predominantly composed of the pyrolyzed PS block. To overcome this problem, films were capped with a SiO₂ layer after UVIN. The capping layer appears to have two advantages – increased areal yields and an improved morphological fidelity. As a result, arrays of nanostructured carbon of great quality were fabricated even at temperatures far above the decomposition temperatures of PS and P2VP blocks.