A Grazing-Incidence SEM Strategy for High-Contrast Imaging of Multiscale Nanomaterials. MoS2 , a Case Study

Scanning electron microscopy (SEM) is a powerful tool for the morphological characterization of multiscale nanomaterials, including two-dimensional (2D) systems such as graphene and molybdenum disulfide (MoS₂). However, conventional SEM imaging often struggles to resolve nanoscale features due to limited contrast and depth sensitivity, especially when dealing with ultrathin layers. In this work, we propose and demonstrate a simple yet effective strategy to overcome these limitations by exploiting grazing-incidence (radent) observation, achieved through a controlled tilting of the sample close to 90°. This approach significantly enhances the emission of secondary electrons from near-surface regions, thereby increasing image contrast and revealing morphological details, such as edges, ripples, defects, and overlapping layers, that remain hidden under standard imaging conditions. Optical characterization of the prepared MoS₂ colloids further supports the formation of monolayer and few-layer sheets, validating the structural information obtained from SEM. Interestingly, this approach recalls natural strategies observed in living organisms, where grazing-angle vision improves edge perception and surface recognition and therefore it can be considered as bio-inspired. Beyond its use with MoS₂, this biomimetic methodology offers a versatile and broadly applicable solution for improving morphological analysis of 2D nanomaterials and thin films, providing deeper insights into their structural characterization.