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(a) HRTEM images of CoPt nanoparticles. Individual Co and Pt atoms appear as additional black contrast on the carbon substrate (see Video 1). The two SNR profiles (right side of the figure) were measured between the two corresponding arrows in the TEM images. The SNR profile 1 shows two Co atoms (SNR of −2.6), whereas the SNR profile 2 shows a Pt atom (SNR of −3.5) (enhanced online) Video 1. [URL: http://dx.doi.org/10.1063/1.4754111.1]10.1063/1.4754111.1
(a) Atomic model used for HRTEM image simulations. The 5 nm-thick carbon film consists in a random arrangement of carbon atoms with atomic distance of 0.142 nm and a film density of 2.2 g/cm2. The white arrow indicates the electron pathway. (b) SNR of the Co (red squares) and Pt (bleu circles) atom measured on the simulated images as a function of the focal distance of the objective lens. The aberration coefficients experimentally calculated by the CEOS corrector software were used for the simulation (two-fold astigmatism <1 nm, three-fold astigmatism = 36 nm, axial coma = 11 nm, and spherical aberration coefficient = 2 μm). (c) Focus stability experimentally measured on an image series of a carbon film recorded with a 2 s time interval. The focal distance was automatically calculated by the corrector software, by using the Thon rings on the fast Fourier transform of each image. The focus instability is mainly due to carbon film oscillations.
Histogram of the single atom SNR experimentally measured between (a) pure Pt NPs and (b) pure Co NPs. (c) CoPt nanoparticles, the two Gaussian peaks centered at −3.24 and −2.52 correspond to the signal of Pt and Co, respectively.
Dynamical behaviour of very small NPs under electron beam irradiation observed at atomic resolution. (a) to (d) Pure Co NPs observed during 4 s. The black arrow in the first image (a) indicates a 2 nm Co NPs that is rapidly shrinking and completely disappears in the last image (d) (see Video 2). (e) to (h) CoPt NPs observed during 10 s. The black arrow in the first image (d) indicates a 2 nm CoPt NPs that is stable and maintains its cohesion (see Video 3) (enhanced online) Video 2; Video 3. [URL: http://dx.doi.org/10.1063/1.4754111.2] [URL: http://dx.doi.org/10.1063/1.4754111.3]10.1063/1.4754111.210.1063/1.4754111.3
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