Combined atomic force‐, friction force‐ and local elasticity microscopy on ReS2 crystals: Surface topography and material contrast

Abstract

AbstractCrystal surfaces of the layered dichalcogenide semiconductor rehenium disulphide (ReS2) grown by the vapour‐phase transport technique were investigated by combined atomic force microscopy (AFM), lateral (friction) force microscopy (LFM) and force modulation (local elasticity) microscopy as well as scanning electron microscopy (SEM). The as‐grown crystals exhibit atomically flat surfaces, on which circular islands with a typical diameter of 0.3 μm and a height of 30–50 nm have grown. While AFM only yields the topographic information, the simultaneously recorded lateral force and force modulation images give a clear material contrast, showing that on the islands the lateral forces are higher and the local elasticity is lower than on the bare ReS2 surface. The dependence of both the topographic and the lateral force images on the scanning direction is investigated. The results indicate that during crystal growth a different material, presumably ReBr3, has segregated on the surface of the ReS2 crystals. It is demonstrated that AFM in combination with LFM and force modulation microscopy can provide information on the composition of heterogeneous samples as well as the local mechanical properties of the different components.