Formation of wrinkles on graphene induced by nanoparticles: Atomic force microscopy study

Wrinkles in monolayer graphene (GN) affect the GN electronic and transport properties. Defined network of wrinkles can be reached by placing the GN on a substrate decorated with nanoparticles (NPs). In order to explain mechanism behind the topographically induced changes of the electronic structure of the GN and to correlate it with the wrinkling, correct description of the GN morphology is of high demand. We propose a methodology based on advanced analysis of atomic force microscopy (AFM) images, which enables determination of the contact/delamination of the GN from the substrate and correlation of the NP density with the character of the wrinkling. Also the relevance of detection of the NPs hidden beneath the GN layer is discussed. The study was carried out on the samples of the GN transferred on the top of SiO2/Si substrate decorated with metal-oxide NPs with nominal diameter of 6 and 10 nm. The NP density varied in the range of ∼20-450 NPs/μm2. The projected area of wrinkles increased linearly with the increasing NP density, independently on the NP diameter.