Copper Oxidation-Induced Nanoscale Deformation of\nElectromechanical, Laminate Polymer/Graphene Thin Films during Thermal\nAnnealing: Implications for Flexible, Transparent, and Conductive\nElectrodes

The transfer of large-area,\ncontinuous, chemical vapor deposition\n(CVD)-grown graphene without introducing defects remains a challenge\nfor fabricating graphene-based electronics. Polymer thin films are\ncommonly used as supports for transferring graphene, but they typically\nrequire thermal annealing before transfer. However, little work has\nbeen done to thoroughly investigate how thermal annealing affects\nthe polymer/graphene thin film when directly annealed on the growth\nsubstrate. In this work, we demonstrate that under improper annealing\nconditions, thermal annealing of poly(ether imide)/single-layer graphene\n(PEI/SLG) thin films on Cu causes detrimental nanoscale structural\ndeformations, which permanently degrade the mechanical properties.\nFurthermore, we elucidate the mechanisms of PEI/SLG deformation during\nthermal annealing and find that permanent deformations and cracking\nare caused by Cu substrate oxidation. This study provides an understanding\nof annealing-induced deformation in polymer/graphene thin films. We\nanticipate that this knowledge will be useful for further developing\ndefect-free, graphene-based thin film electronics.