SEM-Tilting for the Imaging of 2D-Nanomaterials

Owing to their large size and flexibility, 2D-nanostructures (e.g., graphene, graphene oxide, molybdenum bisulfide, etc.) are technologically exploited in a supported form.Glass, silicon and polymers are typical substrates.In the characterization of these 2D-nanostructures, important morphological information (e.g., size, shape factor, presence of defects, etc.) can be obtained by an investigation based on scanning electron microscopy (SEM).However, the observation of layers made by the overlapping of these extremely thin 2D-nanostructures is characterized by a poor contrast and therefore all morphological features are not clearly visible in the SEM micrograph.In this case, atomic force microscopy (AFM) could be conveniently used because of its high sensibility along the z-axis.Here, it has been shown that under a high sample tilting also SEM observations are capable to give images with very good contrast.Such high sample tilting can be obtained by positioning vertically the sample and then reducing conveniently this angle (90) by tilting the sample up to achieve a well-focused image.