Time-resolved compositional mapping during in situ TEM studies

In situ studies using transmission electron microscopy (TEM) can provide insights to how properties, structures and compositions of nanostructures are affected and evolving when exerted to heat or chemical exposure. While high-resolved imaging can be obtained continuously, at video-framerates of hundreds of frames per second (fps), compositional analysis struggles with time resolution due to the long acquisition times for a reliable analysis. This especially holds true when performing mapping (correlated spatial and compositional information). Hence, transient changes are difficult to resolve using mapping. In this work, the time-resolution of sequential mapping using scanning TEM (STEM) and energy dispersive spectroscopy (EDS) is improved by acquiring spectrum images during short times and filtering the spectroscopic data. The suggested algorithm uses regularization to smooth and prevent overfitting (known from compressed sensing) to fit model spectra to the data. The algorithm is applied on simulations as well as acquisitions of catalyzed crystal growth (nanowires), performed in situ in a specialized environmental TEM (ETEM). The results show the improved temporal resolution, where the compositional progression of the different regions of the nanostructure is revealed, here with a time-resolution as low as 16 s compared to the minutes usually needed for similar analysis.