2D materials analysis

Single-layer 2-dimensional materials are actively being investigated across a wide range of fields due to the unique properties they exhibit compared to their bulk equivalents. Materials such as molybdenum disulfide (MoS2) and graphene, for instance, are seeing potential uses in electronics, medicine, and composite materials.

Notably, the properties of 2D materials can be tailored to specific applications through careful modification of their surface chemistry and structure. In order to fully understand these materials and monitor their chemistry, multi-modal observation is often necessary, pairing multiple imaging and analysis techniques to deconvolute molecular-scale changes.

In this application note, single-layer MoS2, deposited on a silicon oxide surface, was analyzed using the Thermo Scientific Correlative Imaging and Surface Analysis (CISA) Workflow.

Combining SEM, EDX, and XPS analysis

The Correlative Imaging and Surface Analysis Workflow combines scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) instrumentation into a single, correlated workflow that can not only provide imaging and surface analysis but also incorporate complimentary techniques, such as Raman spectroscopy.

While SEM can easily visualize 2D materials, these layers are typically too thin to be easily characterized with energy dispersive X-ray (EDX) analysis. XPS, meanwhile, cannot easily resolve surface structures, but can clearly detect what material is present and quantify any chemical changes that might occur to it. XPS instrumentation, like the Thermo Scientific Nexsa G2 Surface Analysis System, can also incorporate a Raman spectrometer that is coincident with the XPS analysis position.

The addition of Raman spectroscopy can enhance the analysis of defects and provide a clear idea of the number of layers of a 2D material that are present. By combining these complementary tools, correlative imaging and surface analysis can provide comprehensive information about the distribution and composition of 2D materials.