Ultra-Clean Freestanding Graphene by Platinum-Metal Catalysis

While freestanding clean graphene is essential for various applications, existing technologies for removing the polymer layer after transfer of graphene to the desired substrate still leave significant contaminations behind. We discovered a method for preparing ultra-clean freestanding graphene utilizing the catalytic properties of platinum metals. Complete catalytic removal of polymer residues requires annealing in air at a temperature between 175 and 350{\deg}C. Low-energy electron holography investigations prove that this method results in ultra-clean freestanding graphene.