With the recent advance of TEM, in-situ observations have become a very essential technique to understand the structure – property relationship of materials. Here, a few examples are shown.  1) Metal silicides are widely used in microelectronics as ohmic contact due to their low resistivity and the existence of phases that are thermodynamically stable over a wide range of temperatures. The fundamental mechanisms about the silicide film formation remains unclear. The formation mechanism of Pd silicide is carefully explored by in–situ HRTEM/ STEM observations in a Cs-corrected TEM, and combined with atomic quantitative analysis (Figure 1).  By in-situ STEM imaging observations, it is found that Pd₂Si is initially formed at the tripe junction at the interfaces, and the formation process is advanced by Pd atom intrusion into Si lattice leading to the Si lattice change. Pd₂Si silicide phase transformation process also induces the strain changes. In addition, the Pd silicide phase transformation process is discussed by the thermodynamics analysis. 2) Simultaneous chemistry and structural transitions are also demonstrated in nanocrystalline materials. Bulk Cu-Cr nanostructures subjected to annealing are shown by in-situ tracking microstructural and compositions enabled with EELS analysis. It is found that the destabilization process of nanostructured materials can initiate at a very low temperature [1], and dynamic process can be well revealed once the composition information is in-situ tracked.

[1]. Acknowledgement: Gabriele Moser and Herwig Felber are gratefully acknowledged for their help with sample preparation. Thank are also given to Rostislav Daniel and Christian Mitterer in Montanuniversität Leoben, Austria for preparing nitride films, and to Olivier Thomas (Aix-Marseille Université) for Pd films. The author is also grateful to Gerhard Dehm (Max-Planck-Institut für Eisenforschung) for  helpful discussion.  

Figures:

Figure. In-situ HRTEM images of Pd silicide formation recorded at 490 °C for 10 mins (a); and at 490 °C for 10 mins for 5 h (b). As can be seen, the Pd silicide grows with holding time while Pd films are gradually reduced.

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EMC Abstracts - https://emc-proceedings.com/abstract/structural-transformations-revealed-by-in-situ-hrtem-observations/