Solvent-free growth of carbon dots by sputter-plasma assisted chemical vapour deposition over large areas

Planar graphene quantum dots synthesized using wet chemistry have been widely investigated for their optoelectronic properties, but less work exists on deposition of curved carbon dots (CDs) by physical techniques. In this work, a bottom-up growth method termed sputter-plasma assisted chemical vapour deposition (SPA-CVD) is used to grow curved CDs in vacuum, reminiscent of graphene fabricated on copper foil using chemical vapour deposition. In SPA-CVD, similar to 10-nm thick Cu layers with an ultrathin carbon film on top are nucleated into copper nanoparticles (Cu-NP) by thermal annealing resulting in curved CDs on their surfaces. CD morphology and dimensions are determined by the hemispherical shape of the nucleated Cu-NPs. With this method, a uniform layer of CDs of tuneable size can be grown on a substrate such as aluminum over wafer-size-areas, without the use of solvents. CD diameter and concentration can be tuned over a wide range by manipulating the SPA-CVD sputtering and evaporation parameters. It is shown that SPA-CVD grown curved CDs embedded in a poly(methyl methacrylate) matrix show resistive memory effects. This work provides a new insight towards the development of high-quality, curved CDs with tuneable properties for device applications, for which planar and solution processed CDs may not be suitable. (c) 2019 Elsevier Ltd. All rights reserved.