TEM instrumentation. Atomic-resolution transmission electron microscopic (TEM) observation was carried out on a JEOL JEM-ARM200F instrument equipped with an aberration corrector (point resolution: 0.10 nm) at 298 K and at an acceleration voltage of E = 80 kV, under 1 ´ 10 -5 Pa in the specimen column. We used a spherical aberration (Cs) value of between 1 and 3 μm, and an electron dose rate (EDR; the number of electrons per second per nm 2 ) of 3.0 ´ 10 5 -3.0 ´ 10 7 e -nm -2 s -1 at ´ 2,000,000 magnification. A series of images were continuously recorded at a frame rate of 50 fps or 75 fps (frame per second) on a CMOS camera (Gatan OneView, In situ mode, D-mode, 4096 ´ 4096 pixels) operating on a binning 4 mode (output image size: 1024 ´ 1024 pixels, pixel resolution 0.021 nm at ´ 2,000,000) or 8 mode (output image size: 512 ´ 512 pixels, pixel resolution 0.042 nm at ´ 2,000,000). For imaging at 200 fps, OneView-IS I-mode operating on a binning 4 mode (output image size: 1024 ´ 1024 pixels, pixel resolution 0.021 nm at ´ 2,000,000). All images were automatically processed on a Gatan DigitalMicrograph software. To record the atomic-resolution movies of the specimens, we first surveyed the whole areas on the grid at low magnification to find specimens suitable for careful analysis. To analyze them in depth, we increased the magnification and started the recording. The images were recorded at under-focus conditions (defocus value: 3 -10 nm). The images were recorded in a .dm4 format using the Gatan DigitalMicrograph software and were transformed into 8-bit or 32-bit .tiff format file by Fiji software . All imaged were filtered by a bandpass filter (filtering structures smaller than 0 -3 pixels and larger than 40 pixels, tolerance of direction: 5%).