Diffusion Induced Different Distributions of Sulfur Clusters on Suspended and Supported Graphene

The distribution of nanoparticles (NPs) on graphene is crucial for the performance of the graphene-based device. Such a distribution would be obviously influenced by the supporting substrates of graphene which are essential for the device. However, there are only a few relevant studies. In this paper, we report the distinct difference in the distributions of sulfur clusters at the submicrometer scale on the suspended graphene compared to a supported one. With vapor deposition of sulfur onto graphene with a patterned substrate, we find that the density of sulfur clusters on the supported regions is 3-8 times larger than that on the suspended ones. While the density decreases as the number of graphene layers increases for the supported regions, the opposite trend is observed within the suspended ones. The density also increases with the area of the suspended regions. The mechanism underlying these phenomena is attributed to the diffusion of small sulfur NPs which coalesce into larger sulfur clusters at the submicrometer scale on graphene, with faster diffusion on the suspended regions due to the more pronounced ripples in suspended graphene. Our results highlight the importance of the supporting substrates and provide guidelines for the fabrication of the graphene-based device.