Temperature dependence of graphene growth on a stepped iridium surface

We have used scanning tunneling microscopy to study the growth of graphene on a periodically stepped Ir(3 3 2) substrate surface, which is a promising route for modification of graphene properties. We have found that graphene continuously extends over iridium terraces and steps. Moreover, new distinctive mesoscopic features of the underlying surface are formed involving large, flat terraces accompanied by groups of narrower steps. The distribution of the newly formed terraces is sensitive to the preparation temperature and only below 800 °C terrace width distribution closer to the intrinsic distribution of clean Ir(3 3 2) are found. We propose that the microscopic shape of steps found after graphene formation is strongly influenced by the orientation of graphene domains, where graphene rotated by 30° with respect to the substrate has a prominent role in surface structuring.