Associate Professor/Lecturer, School of Engineering, Nagoya University
The elucidation of “structures and transformation”, i.e., how atoms configurate solids and how their arrangement changes, is a basic subject in condensed matter physics. Diffraction analyses, such as X-ray methods and various types of static microscopy, have achieved successful outcomes for the former subject “structures,” i.e., the determination of average atomic arrangements of solids in stable states. In contrast, these methods have not provided sufficient contribution in the latter subject “transformation.” Structural dynamics had not been analysed at the atomic scale although it is focused on as a major subject in a tremendous number of studies. This is because even if the structures are analysed in a stepwise fashion during a process, actual structural dynamics is never found out. As a result, continuous atomistic structural dynamics had been studied only via computational science, as exemplified by molecular dynamics calculations. However, the calculated results could not be compared with any experimental results. The development of an innovative experimental method, which can chase the motion of individual atoms in solids as a live broadcast from atomic worlds, had been much awaited in condensed matter physics. Scientists and engineers in this field had also been convinced that the experimental results obtained from the innovative methods lead to the creation of new devices exhibiting noble functions. During an in-situ observation, the observed structures can be controlled. Take, for example, atomic crafts using an in-situ observation as “an eagle eye” and the operation as “small hands and tools.”
We developed in-situ high-resolution transmission electron microscopy (HRTEM) to observe directly atomic motion of solids during mechanical deformation, fracture, phase transformation, surface modulation and interface formation. This developed in-situ HRTEM also enabled simultaneous measurements of conductance of nanostructures and forces acting on them. In particular, the experimental basis of the atomic-scale mechanisms of materials was established.
We applied the in-situ HRTEM to study various nanometre sized structures and elucidated the atomistic structural dynamics during the formation of single atom contacts and wires, which are the finest contacts joined by only one atom and the thinnest wires, i.e., one dimensional single atom alignments, respectively. We explicated the atomic-scale mechanisms of materials for solid point contacts (nanometre-sized contacts), resulting in the discovery of new deformation mechanisms of nanostructures in addition to fundamental atomic process of deformation. Other nanostructures, such as fullerene molecules, carbon nanotubes and single-molecular junction structures, were fruitful targets of the developed in-situ HRTEM.