Short communicationGraphene on graphene formation from PMMA residues during annealing

•In-situ annealing show how PMMA decomposition products migrate on graphene and nucleate additional layers in a dendritic-like fashion.•The dendritic-like growth occurs as layer-by-layer growth of additional graphene sheets.•The grown graphene sheets are randomly oriented on the graphene sheet.

PMMA is a common support material for transferring graphene between substrates. However, PMMA residues typically remain on the graphene sheet after the transfer process. A high temperature annealing process is commonly applied to reduce the amount of PMMA residues. It is also known that high temperature annealing of PMMA causes the PMMA to graphitize, which has been used as a method to synthesize graphene on metal substrates. In this letter we show the development of additional graphene layers during high temperature annealing, which occurs on a single, clean, graphene sheet. The additional graphene is nucleated from the decomposition products of PMMA residues.