  The evolution of the scanning modules for scanning transmission electron
microscopes (STEM) has realized the possibility to generate arbitrary scan
pathways, an approach currently explored to improve acquisition speed and to
reduce electron dose effects. In this work, we present the implementation of a
random scan operating mode in STEM achieved at the hardware level via a custom
scan control module. A pre-defined pattern with fully shuffled raster order is
used to sample the entire region of interest. Subsampled random sparse images
can then be extracted at successive time frames, to which suitable image
reconstruction techniques can be applied. With respect to the conventional
raster scan mode, this method permits to limit dose accumulation effects, but
also to decouple the spatial and temporal information in hyperspectral images.
We provide some proofs of concept of the flexibility of the random scan
operating mode, presenting examples of its applications in different
spectro-microscopy contexts: atomically-resolved elemental maps with electron
energy loss spectroscopy and nanoscale-cathodoluminescence spectrum images. By
employing adapted post-processing tools, it is demonstrated that the method
allows to precisely track and correct for sample instabilities and to follow
spectral diffusion with a high spatial localization.
