We demonstrate a method for phase separating and transferring block copolymer (BCP) nanoscale patterns to arbitrary substrates for surface-independent nanolithography.<sup>1</sup> The enabling technology is a hydrogenated or oxidized graphene thin film that only weakly adheres to its substrate. BCPs are applied to these graphene-based materials and solvent annealed to effect nanoscale phase separation. Then, taking advantage of the weak interaction of the graphene film and its substrate, the BCP/graphene stack is delaminated easily in water. A target substrate is then used to retrieve the stack, which can then serve as a lithographic mask. The use of water as a lift-off agent allows for chemically mild retrieval of the phase-separated BCP, extending the BCP lithography technique to essentially arbitrary substrates. We demonstrate this graphene-enabled BCP lithography on silicon nitride and polyethylene. We also show that using reduced graphene oxide (RGO) as a thin film enables the transfer of wafer-scale BCP films and lithography on SiO<sub>x</sub> and Si. We use an RGO support to produce phase-separated BCP solvent-annealed patterns on polystyrene, a result which is not possible using standard BCP solvent annealing and which shows the utility of this technique. Finally, we will discuss the ability to create nanopatterns of higher complexity by stacking multiple BCP masks, a capability that is not possible using conventional BCP lithography. This technique may have applications in fabricating nanoporous membranes and photonically active coatings.

Graphene-enabled block copolymer lithography transfer to arbitrary substrates

ACS Fall 2021

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